Origin and history of banish

Old English bannan "to summon, command, proclaim," from Proto-Germanic *bannan "to speak publicly" (used in reference to various sorts of proclamations), "command; summon; outlaw, forbid" (source also of Old Frisian bonna "to order, command, proclaim," Old High German bannan "to command or forbid under threat of punishment," German bannen "banish, expel, curse"), apparently a Germanic specialization from a suffixed form of PIE root *bha- (2) "to speak, tell, say" (source also of Old Irish bann "law," Armenian ban "word").

From mid-12c. as "to curse, condemn, pronounce a curse upon;" from late 14c. as "to prohibit;" these senses likely are via the Old Norse cognate banna "to curse, prohibit," and probably in part from Old French banir "to summon, banish" (see banish), a borrowing from Germanic. The sense evolution in Germanic was from "speak" to "proclaim a threat" to (in Norse, German, etc.) "curse, anathematize."

The Germanic root, borrowed in Latin and French, has been productive: banal, bandit, contraband, etc. Related: Banned; banning. Banned in Boston dates from 1920s, in allusion to the excessive zeal and power of that city's Watch and Ward Society. Ban the bomb as a slogan of the nuclear disarmament movement is from 1955.

"lawless robber, brigand" (especially as part of an organized band), 1590s, from Italian bandito (plural banditi) "outlaw," past participle of bandire "proscribe, banish," from Vulgar Latin *bannire "to proclaim, proscribe," from Proto-Germanic *bannan "to speak publicly" (used in reference to various sorts of proclamations), "command; summon; outlaw, forbid" (see ban (v.)).

Vulgar Latin *bannire (or its Frankish cognate *bannjan) in Old French became banir, which, with lengthened stem, became English banish.