Unknown. Possibly related to shag (“shredded tobacco”). The "marijuana" noun sense is attested since the 1980s in the United States, the adjective since the 1990s. The "trinkets or items given away" sense is a variant of swag from 19th century thieves' cant.
- (slang) Low-grade or commercial-grade marijuana.
2002, Joe Babcock, The Tragedy of Miss Geneva Flowers, Closet Case Books, ↑ISBN, page 157:
- The stuff tasted good, better than the usual shwag. I handed him his pipe back, then pulled out my wallet. "Is twenty good?"
- (slang) Alternative form of .
2004, Blaise Cronin, Jeremiad Jottings, Lanham, MD: Scarecrow Press, ↑ISBN, page 91:
- National pride deserves something more than a fistful of freebies from a governmental schwag bag or the wearing of any one of the staggering array of commercially available pins.
schwag (not comparable)
- Jonathon Green (2016), “schwag”, in Green's Dictionary of Slang