"bond money," late 15c., a sense that apparently developed from that of "temporary release from jail" (into the custody of another, who gives security), recorded from early 15c. That evolved from earlier meaning "captivity, custody" (early 14c.). From Old French baillier "to control, to guard, deliver" (12c.), from Latin bajulare "to bear a burden," from bajulus "porter," of unknown origin. In late 18c. criminal slang, to give leg bail meant "to run away."
"to dip water out of," 1610s, from baile (n.) "small wooden bucket" (mid-14c.), from nautical Old French baille "bucket, pail," from Medieval Latin *bajula (aquae), literally "porter of water," from Latin bajulare "to bear a burden" (see bail (n.1)). To bail out "leave suddenly" (intransitive) is recorded from 1930, originally of airplane pilots. Related: Bailed; bailing.
"horizontal piece of wood in a cricket wicket," c.1742, originally "any cross bar" (1570s), probably identical with Middle French bail "horizontal piece of wood affixed on two stakes," and with English bail "palisade wall, outer wall of a castle" (see bailey).
"to procure someone's release from prison" (by posting bail), 1580s, from bail (n.1); usually with out. Related: Bailed; bailing.