smear v.

Middle English smeren, from Old English smerian, smierwan, smyrian "anoint or rub with ointment, oil, etc.," from Proto-Germanic *smerwjan "to spread grease on" (source also of Old Norse smyrja "to anoint, rub with ointment," Danish smøre, Swedish smörja, Dutch smeren, Old High German smirwen "apply salve, smear," German schmieren "to smear;" Old Norse smör "butter"), from PIE *smeru- "grease" (source also of Greek myron "unguent, balsam," Old Irish smi(u)r "marrow," Old English smeoru "fat, grease, ointment, tallow, lard, suet," Lithuanian smarsas "fat").

Originally especially "to anoint," but also in Old English "overspread too thickly with something thick or sticky." In modern use also of bad painting or makeup. The figurative sense of "assault a public reputation" is by 1835; especially "dishonor or besmirch with unsubstantiated charges." Related: Smeared; smearing. Smear-word, one used regardless of its literal meaning but invested with invective, is from 1938.

"mark or stain left by or as if by smearing," 1610s, from smear (v.). The sense of "small quantity prepared for microscopic examination" is from 1903. The meaning "a quantity of cream cheese, etc., smeared on a bagel" is by 1999, from Yiddish shmir.

The earlier noun sense in English is that of "fat, grease; ointment" (c. 1200), from Old English smeoru "fat, grease," cognate with Middle Dutch smere, Dutch smeer, German Schmer "grease, fat" (Yiddish schmir), Danish smør, Swedish smör "butter."