Green’s Dictionary of Slang

(US) a circus performer.

1909		W. Irwin Confessions of a Con Man 82: A circus is always divided into [...] the performers – we call them ‘kinkers’ – and the gamblers.
1943		J.A. Kirch ‘March of the Damned’ in Ten Detective Aces Mar. 🌐 The performers, every last ‘kinker,’ stood frozen like statues.
1946		J.E. Dadswell Hey, Sucker 14: A bunch of dirty-necked ‘kinkers’ or ‘carnies’ unload [...] the handcarved wagons, gaudy geegaws, animals, midgets and human freaks.