c. 1600, "peculiar person, person of a type seldom encountered," from Latin rara avis, literally "strange bird," from rara, fem. of rarus "rare" (see rare (adj.1)) + avis "bird" (see aviary). Latin plural is raræ aves. A phrase used of Horace's peacock (a Roman delicacy), Juvenal's black swan ("Rara avis in terris, nigroque simillima cygno"). A figure perhaps natural to the superstitious Romans, who divined by bird-watching.
"closed end of a passage," 1851 in reference to drainpipes, 1874 in reference to railway lines; by 1886 of streets; from dead (adj.) + end (n.). Figurative use, "course of action that leads nowhere," is by 1914. As an adjective in the figurative sense by 1917; as a verb by 1921. Related: Dead-ended; dead-ending; deadender (by 1996).
1853 in the literal sense (witch-hunting is from 1630s), from witch (n.) + hunt (n.). The extended sense is attested from 1919, American English, later re-popularized in reaction to Cold War anti-Communism.
Senator [Lee S.] Overman. What do you mean by witch hunt?
Mr. [Raymond] Robins. I mean this, Senator. You are familiar with the old witch-hunt attitude, that when people get frightened at things and see bogies, then they get out witch proclamations, and mob action and all kinds of hysteria takes place. ["Bolshevik Propaganda," U.S. Senate subcommittee hearings, 1919]