The noun is attested since 1914, from the colloquial verb smalm, smarm (“to smear, bedaub (hair, with pomade)”), attested since 1847, of unknown origin, perhaps somehow suggestive of the action. Verbal meaning "to smear with flattery" is from 1902.
Practica parlar i memoritzar " smarm " i moltes altres paraules i frases a anglès .