Green’s Dictionary of Slang

(US Jewish) an Italian.

1955		H. Robbins A Stone for Danny Fisher 106: She was a strange kid for a luksh. Usually they were loud and tough and you could tell they were Italian as soon as they opened their mouths.
1983		Maledicta VII 23: In Yiddish-American slang, an Italian was a lukshen and loksh, Yiddish for noodle, i.e. spaghetti.