kittenish adj.

late 14c., kitoun, "the young of a domesticated cat," probably from an Anglo-French variant of Old French chaton, chitoun (Old North French caton) "little cat," a diminutive of chat "cat," from Late Latin cattus (see cat (n.)). In playful use, "a young girl, a sweetheart," from 1870. As a verb, "bring forth kittens," late 15c. To have kittens "lose one's composure" is from 1908.

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.