Origin and history of stag

"adult male of the deer," especially one at 4 or 5 years, late 12c., stagge, which is probably from Old English stagga "a stag," from Proto-Germanic *stag-, from PIE root *stegh- "to stick, prick, sting," and probably so called for its tines. The Old Norse equivalent was used of male foxes, tomcats, and dragons; and the Germanic root word perhaps originally meant "male animal in its prime."

The adjectival meaning "pertaining to or composed of males only" (as in stag party, attested by 1853) is American English slang from 1837 (in stag dance). Compare bull-dance, slang for one performed by men only (1841); gander (n.) also was used in the same sense. Stag film "pornographic movie" is attested from 1968. The stag beetle (1680s) is so called for its branched mandibles, resembling the antlers of a stag.