'unctuous' originates from Latin, specifically the word 'unctuosus,' where 'unctus' meant 'anointed' or 'oily.'

'unctuosus' transformed into the Old French word 'unctueus,' and eventually became the modern English word 'unctuous.'

Initially, it meant 'oily or greasy,' but over time it evolved into its current meaning of 'excessively flattering or ingratiating.'