'turncoat' originates from English, specifically the compound of 'turn' and 'coat', where 'turn' meant 'to change' and 'coat' meant 'a garment'.

'turncoat' changed from Middle English 'turne cote' (literally a 'turned coat') and eventually became the modern English word 'turncoat'.

Initially, it meant 'a coat that could be turned (inside out)' or literally a 'turned coat'; over time it evolved to mean 'a person who changes sides or allegiance'.