Word Origin & History
O.E. impe, impa "young shoot, graft," from impian "to graft," probably an early W.Gmc. borrowing from V.L. *imptus, from L.L. impotus "implanted," from Gk. emphytos, verbal adj. formed from emphyein "implant," from em- "in" + phyein "to plant." Sense of "child, offspring" (late 14c.) came from transfer
of word from plants to people, with notion of "newness" preserved. Modern meaning "little devil" (1580s) is from common use in pejorative phrases like imp of Satan.
"Suche appereth as aungelles, but in very dede they be ymps of serpentes." ["The Pilgrimage of Perfection," 1526]