Yours, Etc.: Origins and Uses of 8 Sign-Offs
"young dog," 1760, shortened form of puppy (q.v.). Used from 1580s for "conceited person." Applied to the young of the fur seal from 1815. Used for "inexperienced person" by 1890. Pup tent (also dog tent) is from 1863. Sopwith pup, popular name of the Sopwith Scout Tractor airplane, is from 1917.
[ultimately fr French poupe´e, ''doll'']