Tolkien envisaged Ælfwine as an Anglo-Saxon who visited and befriended the elves and acted as the source of later mythology. Thus, Ælfwine is given as the author of the various translations in Old English that appear in The History of Middle-earth Series.
The Old English name Ælfwine means “Elf-friend”. It is a well attested historical Germanic name, alongside its Old High German and Lombard equivalents, Alwin and Alboin, respectively.
Source: Ælfwine of England – Wikipedia