Schmear is a word of Germanic origin, equivalent to 'smear' or 'spread' (usually fat or butter). In some Germanic languages, the cognate of smear itself means butter.
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Origin: Before 900; (v.) Middle English: smeren, smirien to rub with fat, anoint; Old English: smirian, smerian, smerwan; cognate with Dutch: smeren; German: schmieren, Old Norse: smyrja, smyrwa; (noun) in current senses derivative of the verb; compare obsolete smear: fat, grease, ointment; Middle English: smere; Old English: smeoru; cognate with Dutch: smear; German: Schmer, Old Norse: smjǫr, Danish: smør - butter; Greek: σμύρις (smýris) - rubbing powder.
The use and spelling schmear or shmear in American English is a direct loanword from Yiddish, where its original usage referred to cheese. In modern usage it has extended to anything that can be spread, such as cream cheese spread upon a bagel. In some cases, it refers to "an entire set or group of related things", or the expression "the whole shmear".
As a slang term, the word shmir in Yiddish also refers to a slap on the face, primarily when disciplining young children.
It can also refer to bribery, as a "little extra" spread on top.