confine v.

c. 1400, "boundary, border, frontier, limit" (usually plural), from Old French confins "boundaries," from Medieval Latin confines "a border, boundary," from Latin confinium (plural confinia) "boundary, limit," from confine, neuter of confinis "bordering on, having the same boundaries," from assimilated form of com "with, together" (see con-) + finis "an end" (see finish (v.)). As "the part of a territory which is near the border" (as in Dryden's "Betwixt the confines of the Night and Day") is from c. 1600.

1620s, "state of being confined; any restraint by force, necessity, or obstacle," from French confinement (16c.; the Old French word was confinacion), from confiner "to border; to shut up, enclose" (see confine).

As "restraint from going abroad by childbirth," perhaps a euphemism for childbed it dates from 1774 (the Middle English expression was Our Lady's bands). To be confined "be unable to leave the house or bed from sickness or childbirth" is attested from 1772.

c. 1600, from un- (1) "not" + past participle of confine (v.).