Green’s Dictionary of Slang

(Irish) one who has sexual intercourse.

1949		J. St Cyr intervew 2 Apr. Association for Cultural Equity q. in E. Wald Jelly Roll Blues (2024) 95: Johnny St. Cyr told Lomax the term [‘Winding Boy’] was ‘a bit on the vulgar side . . . how could I put it? The guy’s a good jazzer’.
1987		(con. 1920s) L. Redmond Emerald Square 95: To wait, with a pile of sods, for some grown up ‘jazzers’ at the Back of the Pipes.