The Collaborative International Dictionary of English v.0.48:

Elf \Elf\ ([e^]lf), n.; pl. Elves ([e^]lvz). [AS. [ae]lf, ylf;
   akin to MHG. alp, G. alp nightmare, incubus, Icel. [=a]lfr
   elf, Sw. alf, elfva; cf. Skr. [.r]bhu skillful, artful, rabh
   to grasp. Cf. 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.
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            Every elf, and fairy sprite,
            Hop as light as bird from brier.      --Shak.
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   2. A very diminutive person; a dwarf.
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   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 (Zo["o]l.), a small owl (Micrathene Whitneyi) of
      Southern California and Arizona.
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