'monotheism' originates from Greek, specifically the word 'monotheos,' where 'mono-' meant 'single' and 'theos' meant 'god.'

'monotheos' transformed into the French word 'monothéisme,' and eventually became the modern English word 'monotheism' through Middle English.

Initially, it meant 'belief in a single god,' and this meaning has largely remained the same in modern usage.