'smarm' originates from Middle English/early modern dialectal words related to Old English/Middle Dutch roots meaning 'to smear' or 'to grease' (compare Middle English 'smeren', German 'schmieren'), where the root 'smer-' meant 'to smear, rub, or grease'.

'smarm' changed from Middle English/Middle Dutch words such as 'smeren' and was influenced by German 'schmieren'; the sense of 'smearing' (literal) developed a figurative sense of 'smoothing over' or 'bowing and flattering', eventually giving the modern English 'smarm'.

Initially, it referred to literal 'smearing' or greasing; over time the meaning shifted metaphorically to 'excessive smoothness or ingratiating flattery' (insincere charm).