In the fourth book of The Chronicles of Narnia, The Silver Chair, Jill and Eustace encounter the largest of all giants, asleep underground.
When they had walked for several miles, they came to a wall of rock, and in it a low archway leading into another cavern. It was not, however, so bad as the last entrance and Jill could go through it without bending her head. It brought them into a smaller cave, long and narrow, about the shape and size of a cathedral. And here, filling almost the whole length of it, lay an enormous man fast asleep. He was far bigger than any of the giants, and his face was not like a giant's, but noble and beautiful. His breast rose and fell gently under the snowy beard which covered him to the waist. A pure, silver light (no-one saw where it came from) rested upon him.
"Who's that?" asked Puddleglum. And it was so long since anyone had spoken, that Jill wondered how he had the nerve.
"That is old Father Time, who once was a King in Overland," said the Warden. "And now he has sunk down into the Deep Realm and lies dreaming of all the things that are done in the upper world. Many sink down, and few return to the sunlit lands. They say he will wake at the end of the world."
The Silver Chair - Chapter 10: Farewell to Shadow-Lands
They see him again, from afar, in the The Last Battle, as he announces the end of the world and summons the stars down from the heavens.
The bonfire had gone out. On the earth all was blackness: in fact you could not have told that you were looking into a wood, if you had not seen where the dark shapes of the trees ended and the stars began. But when Aslan had roared yet again, out on their left they saw another black shape. That is, they saw another patch where there were no stars: and the patch rose up higher and higher and became the shape of a man, the hugest of all giants. They all knew Narnia well enough to work out where he must be standing. He must be on the high moorlands that stretch away to the North beyond the River Shribble. Then Jill and Eustace remembered how once long ago, in the deep caves beneath those moors, they had seen a great giant asleep and been told that his name was Father Time, and that he would wake on the day the world ended.
"Yes," said Aslan, though they had not spoken. "While he lay dreaming his name was Time. Now that he is awake he will have a new one."
Then the great giant raised a horn to his mouth. They could see this by the change of the black shape he made against the stars. After that—quite a bit later, because sound travels so slowly—they heard the sound of the horn: high and terrible, yet of a strange, deadly beauty.
Immediately the sky became full of shooting stars. Even one shooting star is a fine thing to see; but these were dozens, and then scores, and then hundreds, till it was like silver rain: and it went on and on. And when it had gone on for some while, one or two of them began to think that there was another dark shape against the sky as well as the giant's. It was in a different place, right overhead, up in the very roof of the sky as you might call it. "Perhaps it is a cloud," thought Edmund. At any rate, there were no stars there: just blackness. But all around, the downpour of stars went on. And then the starless patch began to grow, spreading further and further out from the centre of the sky. And presently a quarter of the whole sky was black, and then a half, and at last the rain of shooting stars was going on only low down near the horizon.
With a thrill of wonder (and there was some terror in it too) they all suddenly realized what was happening. The spreading blackness was not a cloud at all: it was simply emptiness. The black part of the sky was the part in which there were no stars left. All the stars were falling: Aslan had called them home.
[There follows a plague of monsters and the Last Judgement.]
And out there it began to grow light. A streak of dreary and disastrous dawn spread along the horizon, and widened and grew brighter, till in the end they hardly noticed the light of the stars who stood behind them. At last the sun came up. When it did, the Lord Digory and the Lady Polly looked at one another and gave a little nod: those two, in a different world, had once seen a dying sun, and so they knew at once that this sun also was dying. It was three times—twenty times—as big as it ought to be, and very dark red. As its rays fell upon the great Time-giant, he turned red too: and in the reflection of that sun the whole waste of shoreless waters looked like blood.
Then the Moon came up, quite in her wrong position, very close to the sun, and she also looked red. And at the sight of her the sun began shooting out great flames, like whiskers or snakes of crimson fire, towards her. It is as if he were an octopus trying to draw her to himself in his tentacles. And perhaps he did draw her. At any rate she came to him, slowly at first, but then more and more quickly, till at last his long flames licked round her and the two ran together and became one huge ball like a burning coal. Great lumps of fire came dropping out of it into the sea and clouds of steam rose up.
Then Aslan said, "Now make an end."
The giant threw his horn into the sea. Then he stretched out one arm—very black it looked, and thousands of miles long—across the sky till his hand reached the Sun. He took the Sun and squeezed it in his hand as you would squeeze an orange. And instantly there was total darkness. The Last Battle - Chapter 14: Night Falls on Narnia
This is all there ever is about this giant. However, it always felt to me as a clever reader was supposed to be able to figure out the giant's new name, perhaps by figuring who he corresponds to in Christianity. (That would be how we know that Aslan is Jesus, but that identity is obviously much better documented.)
Blowing the horn that signals the End Times is certainly similar to what the seven angels do in the Book of Revelation, blowing trumpets, one of which calls down the (evil) star Wormwood. However, those angels' names are not, so far as I know, known. The way the giant formerly known as "Time" signals the official beginning of the Apocalypse and destroys the sun is also reminiscent of the role played by Fenrir in Ragnarok, although in that case, the official beginning of Ragnarok is when the Fenris Wolf swallows the sun. It is obviously not a very Christian story, either, although Lewis did incorporate plenty of material from pagan mythology into The Chronicles of Narnia.
So, is it possible to work out the giant's name? And if so, what is it? Or was this merely Aslan (in universe) and Lewis (out of universe) being intentionally mysterious?