impish adj.

Old English impe, impa "young shoot, graft," from impian "to graft," probably an early Germanic borrowing from Vulgar Latin *imptus, from Late Latin impotus "implanted," from Greek emphytos, verbal adjective formed from emphyein "implant," from em- "in" + phyein "to bring forth, make grow," from PIE root *bheue- "to be, exist, grow." Compare Swedish ymp, Danish ympe "graft."

The sense of the word has shifted from plants to people, via the meaning "child, offspring" (late 14c., now obsolete), from the notion of "newness." The current meaning "little devil" is attested from 1580s, from common pejorative phrases such as imp of Satan. The extension from this to "mischievous or pert child" (1640s) unconsciously turns the word back toward its Middle English sense.

Suche appereth as aungelles, but in very dede they be ymps of serpentes. [Wynkyn de Worde, "The Pilgrimage of Perfection," 1526]

adjectival word-forming element, Old English -isc "of the nativity or country of," in later use "of the nature or character of," from Proto-Germanic suffix *-iska- (cognates: Old Saxon -isk, Old Frisian -sk, Old Norse -iskr, Swedish and Danish -sk, Dutch -sch, Old High German -isc, German -isch, Gothic -isks), cognate with Greek diminutive suffix -iskos. In its oldest forms with altered stem vowel (French, Welsh). The Germanic suffix was borrowed into Italian and Spanish (-esco) and French (-esque). Colloquially attached to hours to denote approximation, 1916.

The -ish in verbs (abolish, establish, finish, punish, etc.) is a mere terminal relic from the Old French present participle.