'authenticatable' is formed in modern English by adding the productive adjectival suffix '-able' to the verb 'authenticate'. 'Authenticate' ultimately comes from Greek 'authentikos' via Late Latin 'authenticus' and Medieval Latin 'authenticare'.

'authenticatable' was created from English verb 'authenticate' + '-able'. 'Authenticate' entered English from Medieval Latin/Old French forms derived from Greek 'authentikos' (meaning 'real, genuine'), passing through Late Latin 'authenticus' and Medieval Latin 'authenticare' before becoming the English verb 'authenticate'.

The root originally meant 'real' or 'genuine' in Greek; over time the sense shifted into processes of proving or certifying genuineness. 'Authenticatable' now specifically denotes the capability of being shown or verified as genuine.