Post History

"Bail" derives from the Latin word "baiulus" and came to mean giving property to someone temporarily, a "bailment". Just as prisoners were given to the jail's "baile", they could also be released to someone else's custody, or bail. In order to ensure that they still showed up to trial, a security was required. They weren't seen as being released to be free, but merely transferred to the temporary custody of the person who secured their release. This specific scenario of giving a security to get temporary custody soon overtook the meaning of general jail custody, and it just became known as "bailing someone out of jail".

Once "bail" came to just mean "loaning money as security for the release of a prisoner", it was not a stretch for the bail bond to itself become shortened to just "bail".