Green’s Dictionary of Slang

Zinski n.

[the -zinski ending of many Polish surnames]

(US) a generic name for a Polish immigrant.

[US]S. Ford Torchy 144: They were Zinskis, about twenty of ’em, countin’ women and kids. You didn’t have to look at the tin trunks and roped bundles to know that they’d just finished ten days in the steerage.