Verses with the word buttocks in the Old Testament (3 verses):

2 Samuel 10:4
Wherefore Hanun took David's servants, and shaved off the one half of their beards, and cut off their garments in the middle, even to their buttocks, and sent them away.

1 Chronicles 19:4
Wherefore Hanun took David's servants, and shaved them, and cut off their garments in the midst hard by their buttocks, and sent them away.

Isaiah 20:4
So shall the king of Assyria lead away the Egyptians prisoners, and the Ethiopians captives, young and old, naked and barefoot, even with their buttocks uncovered, to the shame of Egypt.