Green’s Dictionary of Slang

(US) a derog. term for a Chinese person; also adj.

c.1895		George Robey [perf.] ‘The Chinese Laundryman’ 🎵 Ching, ching, Chinaman, I’m a clothes refiner man.
1900		J.I. Markey From Iowa to the Philippines 193: The ‘Chings’ declined to go further forward.
1906		David & Mayo [perf. Sam Mayo] ‘The Chinaman’ 🎵 It's Ching Chang Wing Wang Bing Bang Boo / Known from Piccadilly up to Tim-buc-too.
1912		E. Pugh City Of The World 75: Frenchies, Germans, the whole caboodle of us. Chings, too.
1949		Monteleone Criminal Sl. (rev. edn) 49: ching doll A Chinese girl.
1964		N.B. Harvey Any Old Dollars, Mister? 47: The Ching kid still had his head down.
1971		K. Gilbert Cherry Pickers I i: None of yer racial comment ’ere in my company luv. [...] We’s all the same. Even the Chings!