1914, from colloquial verb smalm, smarm "to smear, bedaub" (the hair, with pomade), 1847, of unknown origin, perhaps somehow suggestive of the action. Verbal meaning "to smear with flattery" is from 1902.
Entries linking to smarm
smarmy adj.
1909, "smooth and sleek;" 1924, "ingratiating, unctuous;" from smarm + -y (2). Related: Smarmily; smarminess.