Adolescent
late Middle English (as a noun): via French from Latin adolescent- ‘coming to maturity’, from adolescere, from ad- ‘to’ + alescere ‘grow, grow up’, from alere ‘nourish’. The adjective dates from the late 18th century.
wiktionary
First attested 1482, from French adolescent, from Latin adolescentem, accusative form of adolescens, present participle of adolēscere(“to become adult, grow up”), from ad-(“to”) + alēscere(“to grow or become nourished”). The adjective first appeared in 1785.
etymonline
adolescent (n.)
mid-15c., "youth, young person, one who is growing up," from French adolescent (15c.) or directly from Latin adolescentem/adulescentem (nominative adolescens/adulescens) "young man or woman, a youth," noun use of an adjective meaning "growing, near maturity, youthful," present participle of adolescere "grow up, come to maturity, ripen," from ad "to" (see ad-) + alescere "be nourished," hence, "increase, grow up," inchoative of alere "to nourish," from a suffixed form of PIE root *al- (2) "to grow, nourish." Adolesce was a back-formed verb used early 20c. (OED quotes H.G. Wells, G.B. Shaw, Louis MacNeice), but it seems not to have taken.
adolescent (adj.)
1785, "growing toward maturity," from Latin adolescentem/adulescentem (nominative adolescens/adulescens) "growing, near maturity, youthful," present participle of adolescere "grow up, come to maturity, ripen" (see adolescent (n.)).
