lower the boom, to

lower the boom, to

To punish severely, to take a decisive action against. This slangy expression, also sometimes used in the meaning of literally delivering a knockout punch, dates from the first half of the 1900s. It alludes to a sailboat’s boom, which can swing wildly in a changing wind. For example, “The bank lowered the boom on Jim and demanded the collateral on his loan.”
See also: lower