Jeor Mormont, Lord Commander of the Night's Watch, was a gruff old man with an immense bald head and a shaggy grey beard. He had a raven on his arm, and he was feeding it kernels of corn. "I am told you can read." He shook the raven off, and it flapped its wings and flew to the window, where it sat watching as Mormont drew a roll of paper from his belt and handed it to Jon. "Corn," it muttered in a raucous voice. "Corn, corn."
A Game of Thrones, Jon III
A "kernel" is a seed or nut from a plant. That includes wheat and other grains. Very broadly speaking though, kernel is usually used more when refering to maize grains rather than other cereals (at least that is what I percieved as a non native speaker). I think that if GRRM wasn't refering maize here, using the expresion "kernels of corn" could be potentially confusing to readers, as they may easily interpret it as maize. I would say this is a weak argument in favour of the possibility that corn=maize, but it should be noted.
And so she rode behind him, beneath the shadow of the Bloody Gate where a dozen armies had dashed themselves to pieces in the Age of Heroes. On the far side of the stoneworks, the mountains opened up suddenly upon a vista of green fields, blue sky, and snowcapped mountains that took her breath away. The Vale of Arryn bathed in the morning light.
It stretched before them to the misty east, a tranquil land of rich black soil, wide slow-moving rivers, and hundreds of small lakes that shone like mirrors in the sun, protected on all sides by its sheltering peaks. Wheat and corn and barley grew high in its fields, and even in Highgarden the pumpkins were no larger nor the fruit any sweeter than here. They stood at the western end of the valley, where the high road crested the last pass and began its winding descent to the bottomlands two miles below. The Vale was narrow here, no more than a half day's ride across, and the northern mountains seemed so close that Catelyn could almost reach out and touch them. Looming over them all was the jagged peak called the Giant's Lance, a mountain that even mountains looked up to, its head lost in icy mists three and a half miles above the valley floor. Over its massive western shoulder flowed the ghost torrent of Alyssa's Tears. Even from this distance, Catelyn could make out the shining silver thread, bright against the dark stone.
A Game of Thrones Catelyn IV
Corn is mentioned alongside wheat and barley. It could mean "generic grain", but it a bit would be strange given that two other grains are specified and that corn appears between them rather than at the end of the list. I think it is also worth mentioning that corn, when describing regions and the crops that appear on them, is only used for The Reach, Riverlands and specially the Vale. If "corn" was used as "generic grain" one would expect that it appeared on more descriptions and not so specifically centered on those 3 regions.
A little farther up the road, they glimpsed a forester's cabin surrounded by old trees and neatly stacked logs ready for the splitting, and later a ramshackle stilt-house leaning over the river on poles ten feet tall, both deserted. They passed more fields, wheat and corn and barley ripening in the sun, but here there were no men sitting in trees, nor walking the rows with scythes. Finally the town came into view; a cluster of white houses spread out around the walls of the holdfast, a big sept with a shingled wooden roof, the lord's towerhouse sitting on a small rise to the west . . . and no sign of any people, anywhere
A Clash of Kings, Arya IV
Same arguments as before: corn appears between two other grains, pointing imo towards maize rather than "generic grain". I think it is also worth metioning that the houses nerbay these fields are white, thus very likely whitewashed, and thus having access to lime, important when processing maize (I will elaborate on this at the end).
"Sausage," said Dirk. "Them long black ones, they're like rocks, they keep for years. I bet he's got a hundred hanging in some cellar."
"Oats," suggested Ollo Lophand. "Corn. Barley."
"Corn," said Mormont's raven, with a flap of the wings. "Corn, corn, corn, corn, corn."
A Storm of Swords, Samwell II
We all know about the crows that constantly demand corn as feed: there are many quotes that fall under this category. What I would like to highlight about this quote is that when enlisting foods "corn" is mentioned, alongside another grain again. It could perfectly mean "generic grain" but there's still a chance that it doesn't.
"We all shed our blood for the Watch. Wear thicker gloves." Jon shoved a chair toward him with a foot. "Sit, and have a look at this." He handed him the parchment.
"What is it?" asked Sam. The raven began to hunt out corn kernels amongst the rushes.
"A paper shield."
A Feast for Crows, Samwell I
Just as the first quote that I listed, the expression "corn kernels" appears again. Could be generic grain, could be maize. In my opinion if it was supposed to be "generic grain" using "corn kernels" is a interesting choice, since it can clearly lead to misinterpretation.
They had no eggs, no more than they had bacon. The Eyrie's granaries held sufficient oats and corn and barley to feed them for a year, but they depended on a bastard girl named Mya Stone to bring fresh foodstuffs up from the valley floor. With the Lords Declarant encamped at the foot of the mountain there was no way for Mya to get through. Lord Belmore, first of the six to reach the Gates, had sent a raven to tell Littlefinger that no more food would go up to the Eyrie until he sent Lord Robert down. It was not quite a siege, not as yet, but it was the next best thing.
A Feast for Crows, Alayne I
Again, another mention of "corn" when describing the production of The Vale, and again listed between mentions of other grains, in my opinion reducing the chances that "corn" is been used as an equivalent of "generic grain" instead of "maize".
"I will." Sam sounded relieved. "My lord, if I might ask … I saw Gilly leaving. She was almost crying."
"Val sent her to plead for Mance again," Jon lied, and they talked for a while of Mance and Stannis and Melisandre of Asshai, until the raven ate the last corn kernel and screamed, "Blood."
"I am sending Gilly away," Jon said. "Her and the boy. We will need to find another wet nurse for his milk brother."
A Dance with Dragons, Jon II
"Corn kernel". I think I said it enough hahahah.
Asha tried to picture herself abed with Erik Ironmaker, crushed beneath his bulk, suffering his embraces. Better him than the Red Oarsman or Left-Hand Lucas Codd. The Anvil-Breaker had once been a roaring giant, fearsomely strong, fiercely loyal, utterly without fear. It might not be so bad. He's like to die the first time he tries to do his duty as a husband. That would make her Erik's widow instead of Erik's wife, which could be better or a good deal worse, depending on his grandsons. And my nuncle. In the end, all the winds blow me back toward Euron. "I have hostages, on Harlaw," she reminded him. "And there is still Sea Dragon Point … if I cannot have my father's kingdom, why not make one of my own?" Sea Dragon Point had not always been as thinly peopled as it was now. Old ruins could still be found amongst its hills and bogs, the remains of ancient strongholds of the First Men. In the high places, there were weirwood circles left by the children of the forest.
"You are clinging to Sea Dragon Point the way a drowning man clings to a bit of wreckage. What does Sea Dragon have that anyone could ever want? There are no mines, no gold, no silver, not even tin or iron. The land is too wet for wheat or corn."
I do not plan on planting wheat or corn. "What's there? I'll tell you. Two long coastlines, a hundred hidden coves, otters in the lakes, salmon in the rivers, clams along the shore, colonies of seals offshore, tall pines for building ships."
A Dance with Dragons, The Wayward Bride
Same as other cases: corn is mentioned alongside another grain, reducing in my opinion the chances of it been used as a synonym of "generic grain".
"Impossible," declared the young maester by Lady Rohanne's side. "Coldmoat supports twenty times as many smallfolk as does Standfast. Her ladyship has fields of wheat and corn and barley, all dying from the drought. She has half a dozen orchards, apples and apricots and three kinds of pears. She has cows about to calf, five hundred head of black-nosed sheep, and she breeds the finest horses in the Reach. We have a dozen mares about to foal."
"Ser Eustace has sheep, too," Dunk said. "He has melons in the fields, beans and barleycorn, and . . ."
The Sworn Sword
Another reference to corn alongside other grains, this time on The Reach.
There is disagreement even on his name. Garth Greenhand, we call him, but in the oldest tales he is named Garth Greenhair, or simply Garth the Green. Some stories say he had green hands, green hair, or green skin overall. (A few even give him antlers, like a stag.) Others tell us that he dressed in green from head to foot, and certainly this is how he is most commonly depicted in paintings, tapestries, and sculptures. More likely, his sobriquet derived from his gifts as a gardener and a tiller of the soil—the one trait on which all the tales agree. "Garth made the corn ripen, the trees fruit, and the flowers bloom," the singers tell us.
The World of Ice and Fire, The Reach: Garth Greenhand
Here it is more than likely that "corn" is in fact "generic grain" anf not maize. Added it just in case
I also looked at the use of "kernel" in the books, to see if the word is used with other grains or exclusively with "corn", suggesting that it in fact refers to maize kernels. All quotes but two ("kernels of truth" and "kernels of knowledge", neither cereals) where kernel is mentioned are alongside corn or in the context of feeding the crows, so it's not bold to assume that corn kernels are the ones that are been talked about. Here are some that I found interesting:
I'm trying, the crow replied. Say, got any corn?
Bran reached into his pocket as the darkness spun dizzily around him. When he pulled his hand out, golden kernels slid from between his fingers into the air. They fell with him.
The crow landed on his hand and began to eat.
A Game of Thrones, Bran III
"Kernels" not only is mentioned alongside "corn", but the colour of said kernels is mentioned too: "gold". Wheat or other grains can have a golden colour, but it is no dobut that maize is very intesly yellow/orange colored, so it's very plausible that they are maize kernels.
Jon's solar was back beyond the racks of spears and shields. He was reading a parchment when Sam entered. Lord Commander Mormont's raven was on his shoulder, peering down as if it were reading too, but when the bird spied Sam it spread its wings and flapped toward him crying, "Corn, corn!"
Shifting the books, Sam thrust his arm into the sack beside the door and came out with a handful of kernels. The raven landed on his wrist and took one from his palm, pecking so hard that Sam yelped and snatched his hand back. The raven took to the air again, and yellow and red kernels went everywhere.
A Feast for Crows, Samwell I
Colour is mentioned again: yellow and red. Unlike golden, yellow is a less common way of describing wheat, barley or other grains. Red wheat exists, having a more "toasted" appereance. Its colour is given by the husk, tho the seeds can be a bit rusty toned too. Maize on the other hand has very prominent and known varieties with intense and clearly yellow/red coloring. The possibility that those kernels aren't maize is honestly slim. If that was the case the chances that the corn fed to crows during the whole series is indeed maize is very high.
