It also appears in other 'blaxplotion'-movies. In the movie 'Undercover brother' which is a parody to this movies it appears too.
Phrase made popular in mainstream culture by the classic 70's film the Warriors.
Was used before though by the hippie counterculture; for example Arlo Guthrie said it a couple of times during his apperance at Woodstock.
(youtube it) - Arlo Guthrie WOODSTOCK 1969 - Walking Down The Line
That sucks dude, ill throw you some bills though. shit happens, can you dig it?
Yea man, fuckin a