jail-break n.

c. 1300 (c. 1200 in surnames) "a jail, prison; a birdcage." The form in j- is from Middle English jaile, from Old French jaiole "a cage; a prison," from Medieval Latin gabiola "a cage," from Late Latin caveola, diminutive of Latin cavea "a cage, enclosure, stall, coop; a hollow place, a cavity" (see cave (n.)).

The form in g- was the more usual in Middle English manuscripts (gaile, also gaiole), from Old French gaiole "a cage; a prison," a variant spelling that seems to have been frequent in Old North French, which would have been the system familiar to Norman scribes. Now pronounced "jail" however it is spelled. Persistence of gaol (preferred in Britain) is "chiefly due to statutory and official tradition" [OED], and, probably, the fact that it is known the Americans spell it the other way.

In U.S. usually a place of confinement for petty offenders. The Medieval Latin word also is the source of Spanish gayola, Italian gabbiula.

c. 1300, "act of breaking, forcible disruption or separation," from break (v.). The sense in break of day "first appearance of light in the morning" is from 1580s; the meaning "sudden, marked transition from one course, place, or state to another" is by 1725.

The sense of "short interval between spells of work" (originally between lessons at school) is from 1861. The meaning "stroke of luck" is attested by 1911, probably an image from billiards (where the break that scatters the ordered balls and starts the game is attested from 1865). The meaning "stroke of mercy" is from 1914. The jazz musical sense of "improvised passage, solo" is from 1920s. The broadcasting sense is by 1941.