"trash," 1915, from American Yiddish shlak, from German Schlacke "dregs, scum, dross" (see slag, n.). Alternative etymology [OED] is from Yiddish shlogn "to strike" (cognate with German schlagen; see slay). Derived form schlockmeister "purveyor of cheap merchandise" is from 1965. Adjectival form schlocky is attested from 1968; schlock was used as an adjective from 1916.