'monotonous' originates from Greek, specifically the word 'monotonos,' where 'mono-' meant 'single' and 'tonos' meant 'tone.'

'monotonos' transformed into the Late Latin word 'monotonus,' and eventually became the modern English word 'monotonous.'

Initially, it meant 'having one tone,' but over time it evolved into its current meaning of 'dull and repetitive.'