at liberty

late 14c., "free choice, freedom to do as one chooses," from Old French liberté "freedom, liberty, free will" (14c.), from Latin libertatem (nominative libertas) "freedom, condition of a free man; absence of restraint; permission," from liber "free" (see liberal)

Nautical sense of "leave of absence" is from 1758. To take liberties "go beyond the bounds of propriety" is from 1620s. Sense of "privileges by grant" (14c.) led to sense of "a person's private land" (mid-15c.), which yielded sense in 18c. England and America of "a district within a county but having its own justice of the peace," and also "a district adjacent to a city and in some degree under its municipal jurisdiction" (e.g. Northern Liberties of Philadelphia). Also cf. Old French libertés "local rights, laws, taxes."