'monotrichous' originates from New Latin (scientific coinage), ultimately from Greek, specifically from the elements 'mono-' (from Greek 'monos') and 'trich-' (from Greek 'thrix'/'trichos'), where 'mono-' meant 'single' and 'trich-' meant 'hair'.

'monotrichous' was formed in New Latin/scientific usage from Greek elements 'monos' + 'thrix' (hair), adapted as a New Latin/Neo-Latin term and eventually entered modern English as 'monotrichous'.

Initially it meant 'single-haired' in a literal sense, but over time it became a technical biological term meaning 'having a single flagellum' or 'bearing one hairlike appendage'.