exclamation of contempt, 1817, probably from French bah, Old French ba, expressing surprise, scorn, dismay. Perhaps simply a natural exclamation in such situations; compare Greek babai!, an exclamation of surprise. De Quincey condemned it as a coarse French import.
Twenty five years ago the vile ejaculation "Bah!" was utterly unknown to the English public. Now, and entirely through the currency given to it by our own novels, it has become the most popular expression for dismissing with contempt any opinion or suggestion of the person with whom you are conversing. Sir Edward Lytton was amongst the earliest and deepest offenders. ["French and English Manners," 1850]
"horizontal piece of wood in a cricket wicket," c. 1742, originally "a cross bar" of any sort (1570s), probably identical with French bail "horizontal piece of wood affixed on two stakes," and with English bail "palisade wall, outer wall of a castle" (see bailey). From 1904 as the hinged bar which holds the paper against the platen of a typewriter.
"bond money, security given to obtain the release of a prisoner," late 15c., a sense that apparently developed from that of "temporary release (of an arrested person) from jail" (into the custody of another, who gives security for future appearance at trial), which is recorded from early 15c. That seems to have evolved from the earlier meanings "captivity, custody" (late 14c.), "charge, guardianship" (early 14c.).
The word is from Old French baillier "to control, to guard, deliver" (12c.), from Latin baiulare "to bear a burden," from baiulus "porter, carrier, one who bears burdens (for pay)," which is of uncertain origin; perhaps a borrowing from Germanic and cognate with the root of English pack, or perhaps from Celtic. De Vaan writes that, in either case, "PIE origin seems unlikely."
To go to(or in) bail "be released on bail" is attested from mid-15c. In late 18c. criminal slang, to give leg bail meant "to run away."
To bail out "leave suddenly" (intransitive) is recorded from 1930, originally of airplane pilots. Perhaps there is some influence from bail (v.2) "procure (someone's) release from prison." Related: Bailed; bailing.
Middle English baylle, "wall enclosing an outer court" of a castle, fortified city, etc. (c. 1200 in Anglo-Latin, late 13c. in place-names), a variant of bail, from Old French bail "stake, palisade, brace," which is of unknown origin, perhaps ultimately connected to Latin bacula "sticks," on notion of "stakes, palisade fence."
The word was extended to mean the outer court itself (early 14c.). Hence Old Bailey, seat of Central Criminal Court in London, so called because it stood within the ancient bailey of the city wall. The surname Bailey usually is from Old French bailli, a later form of baillif (see bailiff). Bailey's, the Irish whiskey- and cream-based liqueur, was introduced in 1974 and said to have been named for the historic Bailey's Hotel in London.