Webster's Revised Unabridged Dictionary · 1913

Elf

Elf (elf) , noun

[Anglo-Saxon alf, ylf; akin to Middle High German alp, German alp nightmare, incubus, Icelandic ālfr elf, Swedish alf, elfva; compare Sanskrit rbhu skillful, artful, rabh to grasp. Compare Auf, Oaf.]

1.
An imaginary supernatural being, commonly a little sprite, much like a fairy; a mythological diminutive spirit, supposed to haunt hills and wild places, and generally represented as delighting in mischievous tricks.
Every elf, and fairy sprite, Hop as light as bird from brier. — Shakespeare
2.
A very diminutive person; a dwarf.
Collocations (4)
Elf arrow , a flint arrowhead; -- so called by the English rural folk who often find these objects of prehistoric make in the fields and formerly attributed them to fairies; -- called also elf bolt, elf dart, and elf shot.
Elf child , a child supposed to be left by elves, in room of one they had stolen. See Changeling.
Elf fire , the ignis fatuus. — Brewer
Elf owl (Zoology) , a small owl (Micrathene Whitneyi) of Southern California and Arizona.

Elf , transitive verb

To entangle mischievously, as an elf might do.
Elf all my hair in knots. — Shakespeare