Today it means: Possessing physical features, behaviors, personality traits or other properties that are mainly attributed to infants and small or cuddly animals; e.g. fair, dainty, round, and soft physical features, disproportionately large eyes and head, playfulness, fragility, helplessness, curiosity or shyness, innocence, affectionate behavior. Full definition →
Aphetic form of acute, originally meaning “keenly perceptive or discerning, shrewd” (1731). Meaning transferred to “pretty, fetching” by US students (slang) c. 1834. Meaning drifted further to describe the pleasing attraction to features usually possessed by the young.
Etymology from Wiktionary, CC BY-SA 4.0.