'turncoatism' originates from English, specifically the compound 'turncoat' with the suffix '-ism', where 'turn-' meant 'to change (one's position)' and 'coat' referred to 'coat' (originally the garment indicating allegiance), and '-ism' meant 'practice or doctrine'.

'turncoatism' changed from the Modern English compound 'turncoat' (itself derived from the phrase 'to turn one's coat' used to describe switching allegiance) and was formed by adding the abstract-noun suffix '-ism' to create a term for the practice or tendency.

Initially, related expressions referred literally to turning one's coat (changing the garment); over time the meaning shifted to changing political or personal allegiance, and 'turncoatism' evolved to mean the practice or tendency of such switching.