Green’s Dictionary of Slang

bootchkey n.

also butchski, butchsky, butski
[Czech pockej, wait, used by Czech youngsters while playing games and thus adopted as generic by early Eastern European immigrants to US]

(US) a Czech immigrant.

[US]T. Čapek Čechs in America 114: In some localities Bohemians are called ‘Bohoes’, in others ‘Bohunks’; less familiar are the terms ‘Cheskey’ and ‘Bootchkey’ .
A.A. Roback Dict. International Slurs (1979) 22: Bootchkey: A Czech. Apparently from pockej, (hold on) which the boys cry at play. (American slang).
[US]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.
[US]I.L. Allen Lang. of Ethnic Conflict 54: czechs [...] bootchkey [or butchski, butski. Roback says from pockej, ‘hold on,’ a children’s cry].