"young German noble," 1550s, from German Junker, from Old High German juncherro, literally "young lord," from junc "young" (see young (adj.)) + herro "lord" (see Herr). Pejorative sense of "reactionary younger member of the Prussian aristocracy" (1865) is from Bismarck's domestic policy. Related: Junkerism. Meaning "drug addict" is from 1922; that of "old worn-out automobile" is from 1969, both from junk (n.1).

Roman goddess of adult women and marriage, sister and wife of Jupiter, mid-14c., probably literally "the young one" (if so, perhaps as goddess of the new moon), from Proto-Italic *juwen- "young," which also is the source of Latin iunior "younger," iuvenis "young man" (see young (adj.)). Noted for her stately beauty and fits of jealous rage. Also the patron of national finances. Usually identified with Greek Hera, but Juno also had qualities of Athena.

1580s, "a younth, a young man, a juvenile," from noun use of Latin iuvenalis "youthful, suitable for young persons," from iuvenis "young man" (see young (adj.)). The Roman satirist is Decimius Junius Juvenalis. As an adjective from 1630s.

1759, "becoming young, growing young in appearance," from Latin iuvenescentem (nominative iuvenescens), present participle of iuvenescere "to grow into youth, grow young again, regain youth," from iuvenis "young man" (see young (adj.)). Its use in a sense of "immature, undeveloped" (by 1875) is etymologically incorrect.

1620s, "young, youthful," from Latin iuvenilis "of or belonging to youth, youthful," from iuvenis "young man, one in the flower of his age" (in Roman use, the period just beyond adolescence, from age 21 or 25 to 40), noun use of an adjective meaning "young" (source also of French jeune; see young (adj.)).

Meaning "pertaining to or suited to youth" is from 1660s. As a noun, "a young person," from 1733. Juvenile delinquency first recorded 1816; Juvenile delinquent the following year. Slang shortening juvie/juvey is recorded from 1941 as "juvenile delinquent," 1967 as "juvenile detention."

1620s, "state of being young or youthful," from Latin iuvenilitas "youth," abstract noun from iuvenilis "of youth," from iuvenis "young man" (see young (adj.)). Meaning "anything characteristic of youth" is from 1660s; that of "juveniles collectively" is from 1823.

Roman god of youth, personification of iuventas "youth, young person," originally "the age of youth" (from 20 to 40), from iuvenis "young man" (see young (adj.)).

"restore the appearance, powers, or feelings of youth to," 1807, an irregular formation from re- "again" + Latin juvenis "young" (see young (adj.)) + -ate (2). Related: Rejuvenated; rejuvenating.

"renewal of the appearance, powers, or feelings of youth," 1630s, from Latin rejuvenescere "become young again," from re- "again" (see re-) + juvenescere "become young," from juvenis "young" (see young (adj.); also see -ence).

1580s, from young (adj.) + -ster. Earlier was youngling, from Old English geongling.