'barnumism' originates from English, specifically the name 'Barnum' (from P. T. Barnum), combined with the suffix '-ism' borrowed from Greek via Latin and French, where '-ism' meant 'practice or system'.

'barnumism' changed from the phrase 'Barnum statement' and the related term 'Barnum effect', and eventually became the modern English word 'barnumism' used to describe vague flattering statements.

Initially, it meant 'promotional trickiness or flamboyant claims associated with P. T. Barnum', but over time it evolved into its current meaning of 'a vague, general, flattering statement that seems personal but applies to many'.