yoke: the wooden bar fastened over the neck of a draft animal, and by extension the burden of subjection it pictures
A yoke is the wooden frame or bar laid across the necks of oxen so they pull a plow or cart together under a farmer's control. The word names that physical implement, and nearly every other use in the Bible grows out of that single picture.
From the animal's neck the image moves to people. To be under a yoke is to be under someone else's control: the forced labor, taxes, and hard service that a conquering king lays on a subject people. This is the most common use, from Rehoboam's threat to make Israel's yoke heavier to the prophets' promise that God will one day snap the yoke of Babylon off his people's necks.
The same picture also describes life under God. His rightful claim on his people is a yoke to be carried in obedience, one the rebellious throw off, and the hardship he sends is a yoke a person does well to bear patiently rather than fight.