Green’s Dictionary of Slang

(US) a derog. term for a Czech immigrant.

1920		T. ?apek ?echs in America 114: In some localities Bohemians are called ‘Bohoes’, in others ‘Bohunks’; less familiar are the terms ‘Cheskey’ and ‘Bootchkey’ .
1945		Mencken Amer. Lang. Supplement I (1975) 602: In regions where Czech immigrants are numerous cheskey is frequently heard. Monsignor Dudek says that it is ‘an attempted transliteration of the Bohemian adjective cesky (Czech).’.
1950		WELS.
1964		PADS 42 40: Both of the very old forms czezski (or chesky) and butchsky were offered by an old German who remembered using those terms in her youth on the West Side of Chicago.