Etymology of Kobold

At page 239. of Mr. Bohn's edition of Keightley's *Fairy Mythology*, we find that Mr. K., after heading a chapter with "Kobolds," says in a note:— "This word is usually derived from the Greek κόβαλος, a knave, *but as this is only found in lexicographers*, it may in reality be a Teutonic word in a Greek form." Surely, Mr. Keightley has forgotten the following passages— 1. Ar. Equites, 450. Dindf. [Conf. Ranæ, 1015.] "ΚΛΕΩΝ: κόβαλος εἶ. ΑΛΛ. πανοῦργος εἶ." 2. Ejusdem fab., 635.: "Βερέσχεθοί τε καὶ κόβαλοι καὶ Μόθων." 3. Plutus, 279.: "ὡς μόθων εἶ τε καὶ φύσει κόβαλος." 4. Aristotle, *H. A.* 8.…