Oaf \Oaf\ ([=o]f), n. [See Auf.]

Originally, an elf's child; a changeling left by fairies or goblins; hence, a deformed or foolish child; a simpleton; an idiot.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Auf \Auf\ ([add]f), n. [OE. auph, aulf, fr. Icel. [=a]lfr elf. See Elf.]

[Also spelt oaf, ouphe.]

A changeling or elf child, -- that is, one left by fairies; a deformed or foolish child; a simpleton; an oaf. [Obs.]

--Drayton.

Source: Webster's Revised Unabridged Dictionary (1913)