Pipe Down: This originally nautical term was used as an officer's whistle sound denoting the completion of an above-deck work shift and thereby giving permission to go below. This expression is now used to mean "be quiet" or keep quiet".

Yes. It took about three minutes to come up with this similar definition.

All references I find to "Blow the man down" state that it means "To kill someone".

But they're wrong.
Cheers.
Jim

p.s. Those who really do know the answer are probably enjoying watching me flounder here!