Although elfs may occasionally be found in print the accepted modern plural form of elf is elves. This follows the common method of pluralizing nouns in English ending in an –f (shelf/shelves, calf/calves). There are, it should be noted, numerous exceptions to this, such as roof/roofs, and serf/serfs.
Why are elves associated with Christmas?
Elves began to be associated with Christmas in the United State in the 19th century, following the publication of such works as Clement Clarke Moore’s 1823 poem "A Visit from St. Nicholas," which described the titular figure as "a right jolly old elf."
What is the origin of the word elf?
Elf is a very old word, and has been with us not only in modern English, but in Middle and Old English as well (in Old English it was ælf). Dating in use from before the 12th century, elf has similarities to a number of related words in other languages, such as the Middle Low German alf ("incubus") and the Old Norse alfr ("elf").