The Prose Edda 1.7

Then said Gangleri: "What covenant was between them, or which was the stronger?" And Hárr answered: "The sons of Borr slew Ymir the giant; lo, where he fell there gushed forth so much blood out of his wounds that with it they drowned all the race of the Rime-Giants, save that one, whom giants call Bergelmir, escaped with his household; he went upon his ship, and his wife with him, and they were safe there. And from them are come the races of the Rime-Giants, as is said here:

Untold ages ere earth was shapen, Then was Bergelmir born; That first I recall, how the famous wise giant On the deck of the ship was laid down."