Meaning

noun the shape or manner in which things come together and a connection is made

noun a set containing all and only the members of two or more given sets

verb become part of; become a member of a group or organization

originFrom Middle English joinen, joynen, joignen, from Old French joindre, juindre, jungre, from Latin iungō (“join, yoke”, verb), from Proto-Indo-European *yewg- (“to join, unite”). Cognate with Old English iucian, iugian, ġeocian, ġyċċan (“to join; yoke”). More at yoke.

Etymology from Wiktionary, CC BY-SA 3.0