Pup

google

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late 16th century (in the sense ‘arrogant young man’): back-formation from puppy, interpreted as a diminutive.

wiktionary

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From a shortening of puppy.

etymonline

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pup (n.)

1760, "young dog," shortened form of puppy (q.v.). Used earlier (from 1580s) for "conceited person," from the figurative sense of puppy. An English-Latin wordbook from late 15c. for Latin pupa gives English pup-bairn. Applied to the young of the fur seal from 1815. Used for "inexperienced person" by 1890.

Pup tent (also dog tent) as a type of small tent used in the military is from 1863. Sopwith pup, popular name of the Sopwith Scout Tractor airplane, is from 1917.