bobby soxyoudaoicibaDictYouDict
1943, from diminutive of bob (n.2) + sox. So called because they are "shortened" compared to knee-socks. Derivative bobby-soxer first attested 1944.
Months ago colored bobby sox folded at the top were decreed, not by anyone or any group but, as usual, by a sudden mysterious and universal acceptance of the new idea. Now no teen-ager dares wear anything but pure white socks without a fold. ["Life" magazine, Dec. 11, 1944]
poser (n.)youdaoicibaDictYouDict
"one who practices an affected attitude," 1881, agent noun from pose (v.1); revived in teen-ager slang by 1983. Meaning "question that puzzles" is from 1793 from pose (v.2); earlier it meant "one who asks testing questions" (1580s).
teen (n.)youdaoicibaDictYouDict
"teen-aged person," 1818 (but rare before 20c.), from -teen. As an adjective meaning "of or for teen-agers," from 1947.
teenager (n.)youdaoicibaDictYouDict
also teen ager, teen-ager; 1922, derived noun from teenage (q.v.). The earlier word for this was teener, attested in American English from 1894, and teen had been used as a noun to mean "teen-aged person" in 1818, though this was not common before 20c.