The name Ælfwine simply means "Elf-friend", and is the Old English equivalent of Elendil. The names Elvis and Alvin are modern descendants. It is possibly intended as a cognate of Albion.
Although there is no such framework in the published version of The Silmarillion, some of the later writings of Tolkien indicate that he didn't fully abandon the idea of a framework. However, although Ælfwine is still referred to in some post-Lord of the Rings writings, Tolkien ultimately changed the intended framework of The Silmarillion from the tale of Ælfwine to one based around Bilbo Baggins' edits of "Elvish lore".
Ælfwine is also given as the author of the various translations in Old English that appear in the History of Middle-earth series. A minor discrepancy is that whereas Ælfwine is described as hailing from the north-west of England, his Old English texts are in the Mercian dialect, which was Tolkien's favourite.
Eriol is a mysterious enigma that appears at the beginning of the third season.
As it usually happens, Eriol is a transfer student in Sakura's class and the first person that his eyes travel to among the students in the classroom is Sakura.
Eriol's whole purpose is unknown to everyone until the very end of the series, where he exposes his true identity and purpose in coming to Tomoeda and relentlessly testing Sakura's strength as the master of the Clow Cards.