Meaning

adjective united or combined

noun (anatomy) the point of connection between two bones or elements of a skeleton (especially if it allows motion)

verb fit as if by joints

originThe noun is from Middle English joynt (attested since the late 13th century), from Old French joint (“joint of the body”) (attested since the 12th century). The adjective (attested since the 15th century) is from Old French jointiz. Both Old French words are from Latin iūnctus, the past participle of iungō. See also join, jugular, junction. Displaced Old English fōg and partially displaced…

Etymology from Wiktionary, CC BY-SA 3.0