Other Words for A$$ in American English

"Ass" is not appropriate for polite  company. So what other words are used?

The medical term or technical term is "buttocks."

In everyday conversation, I might say:

I fell on my butt.

I fell on my backside. I

I fell on my rear end.

Babies are cute, right? So it's easy to  understand the idiom "smooth as a baby's bottom."

How about "bum?" Wouldn't it be  awful if a bug bit you on the bum?

"Derrière" is a polite term.

When we want to sound funny or  cute, we have a lot of words:  

heinie, keister, fanny, tail end,  wazoo. Well, there's probably more.

If someone says you have nice buns or hot buns,  

it's a compliment, but it's  probably not appropriate.

An angry person might give an order like this:

Sit your behind down.

Get your rear end over here.

My kids told me that their bus driver used  to tell them, "Keep your tushy on the cushy!"

So "tushy" is like your backside.  Tushy. Tush. And then "cushy" just  

rhymed. And "cushy" referred to  the seat, the cushion of the seat.

Keep your tushy on the cushy.