IDIOM ►

lower the boom

Meaning 1
to put the boom of a sailboat down (See DERIVATION below for definition of "boom")
Sentence 1
Lower the boom as we come into the harbor. We won't need as much wind.
Meaning 2
to reprimand, scold or get angry at someone
Sentence 2
Joe was not performing at work. The boss lowered the boom on him. He told him to improve his work or he would be fired.

Derivation

The boom is a heavy piece of wood or metal attached to the mast of a ship to which the sail is attached. Sailors must be careful to watch the boom when it is lowered or they might be hit on the head.