'perfectionist' is formed in modern English from the noun 'perfection' + the agent suffix '-ist'. 'Perfection' comes from Latin 'perfectio' (from 'perfectus', the past participle of 'perficere'), where 'per-' meant 'through/complete' and 'facere' meant 'to do/make'.

'Perfectionist' developed from Latin and Old French influences: Latin 'perficere' → Late Latin 'perfectio' → Old French/Middle English forms of 'perfect'/'perfection' → modern English 'perfection' + suffix '-ist' produced 'perfectionist' in the 19th century English usage.

Originally the root referred to the state or act of making something complete ('perfection'). Over time, the derived noun 'perfectionist' came to mean 'a person who pursues or demands perfection', and it later acquired a sometimes negative sense of being excessively particular or critical.