'authentical' originates from Late Latin, specifically the word 'authenticus', which came from Greek 'authentikos' where 'authentes' meant 'one acting with authority'.

'authentical' changed from the Late Latin 'authenticus' through Old French 'authentique' into Middle English and eventually the modern English adjective 'authentical' (now usually replaced by 'authentic').

Initially, it meant 'having authority' or 'authoritative', but over time it evolved into the current primary sense 'genuine; real'.