Extremely old jargon for a dealer. The only reason I know is because there is a song about it on the soundtrack to Easy Rider.
Even when I was a young adult mom hated that song. The dealer sells you a lot of sweet dreams but the pusher is a monster. God damn the pusher man. I may not have the words exactly right but I wore out many a cassette and a few LP's of that sound track. Mom didn't like taking the Lord's name in vain, couldn't argue with her there. On the other hand while I wasn't all that impressed with the movie, for many years I thought that was the best sound track, the entire cassette, ever!
A bit of trivia, I was born on a forty acre farm a few miles from where Jack Nicholson was killed, next to some property my cousin owned in the Morganza Spillway. Family friends, the Melancon's owned the little cafe in Morganza where the trouble started. We often got together to fry fish or other family get togethers with them. Small world!
Hu