'attaint' originates from Old French, specifically the word 'ataindre' (past participle 'ataint'), ultimately from Latin roots meaning 'to touch/reach' (see below).

'attaint' changed from Old French 'ataint' (past participle of 'ataindre') into Middle English forms such as 'atteinten'/'attainten' and eventually the modern English 'attaint' (used especially in legal contexts).

Initially it meant 'to touch' or 'to reach' (in a concrete sense), but over time it evolved into legal and figurative senses like 'to affect with guilt, to condemn, or to taint,' which are reflected in later English usage.