not say boo idiom
US informal什么也没说，一言未发
to say nothing
You didn't say boo to me about going to your mother's this weekend. 你从没和我提起过这个周末要去你母亲家的事情。
US informal (also be afraid to say boo); (UK not say boo to a goose)非常胆小
to be very nervous and easily frightened