From Latin 'jungere' (to yoke), from PIE *yewg- — same root as 'yoke,' both from yoking animals together.
To link or connect; to come together with; to become a member of a group or organization.
From Old French joindre (to join, connect, unite), from Latin jungere (to join, yoke, harness), from PIE *yewg- (to join, to yoke). This PIE root is one of the most widely distributed in the family: Sanskrit yuj- (to yoke, unite — the root of yoga), Greek zeugma (a yoking, a rhetorical figure), Latin jugum (yoke, also in conjugal), and English yoke through Proto-Germanic *yukam. The conceptual domain covers both the act of yoking animals together (the primary agricultural sense) and the union of anything — people in marriage,
English has both 'join' (from Latin 'jungere' through French) and 'yoke' (from Old English 'geoc,' from Proto-Germanic '*juką') — and both descend from the same PIE root *yewg- (to join). They are Indo-European doublets separated by five thousand years and two completely different transmission paths. The yoking of oxen was so fundamental to early Indo-European agriculture that the word for it survived