背中を洗ってくださいよ。

back (of body)

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to wash; to investigate

to give; to confer; to bestow; to kindly do for one; to oblige; to favour; to favor

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!