Википедия в статье о нем сообщает, что
Tolkien learned Latin, French, and German from his mother, and while at school he learned Middle English, Old English, Finnish, Gothic, Greek, Italian, Old Norse, Spanish, Welsh, and Medieval Welsh. He was also familiar with Danish, Dutch, Lombardic, Norwegian, Russian, Serbian, Swedish and older forms of modern Germanic and Slavonic languages, revealing his deep linguistic knowledge, above all of the Germanic languages.
Не буду все переводить - в общем, знал он языки.