From Middle English yok, yoke, ȝok, from Old English ġeoc, from Proto-Germanic *juką, from Proto-Indo-European *yugóm, from *yewg-. yuga.
Senses 3.1 (“area of arable land”) and 3.2 (“amount of work done with draught animals”) probably referred to the area of land that could generally be ploughed by yoked draught animals within a given time.