This halyard shanty came across the Atlantic derived from an African work song called "Knock a Man Down". The "blow" referred to in the song is the striking of a man, not the verb you were thinking of.
We did a version of this song on our first recording with a tamer set of lyrics.
This version is more loaded with not-so-subtle innuendo and more likely the type of lyrics you would hear bawdy sailors singing while heaving a line.