famous last words idiom informal
吹牛，说得煞有介事；不见得，那倒不一定
said when someone makes a statement that is shown very soon, and in an embarrassing way, to be wrong
I told him categorically that we could never be anything more than friends. Famous last words! Within a few months we were engaged. 我明确告诉他我们只可能做朋友。说得跟真的似的，可才过了几个月我们就订婚了！