Green’s Dictionary of Slang

slinger n.

[sling v.]

1. [mid-19C+] (US) a waiter or waitress.

2. [1910s+] as sfx, denoting a variety of worker.

3. [1940s–50s] (UK Und.) one who passes forged notes .

4. [1980s+] (US Und., a drug dealer; thus S.Afr.) bum-slinger, a seller of second-rate drugs.