'unappealability' originates from Modern English, specifically formed from the negative prefix 'un-' (from Old English 'un-' meaning 'not'), the noun 'appeal' (from Anglo-French/Old French 'apel' < Latin 'appellare'), and the suffix '-ability' (from French/Latin '-abilitas' meaning 'capacity or suitability').

'appeal' comes from Latin 'appellare' (to call upon, address) which passed into Old French as 'apel' and Middle English as 'appellen'/'appeal'; the productive English suffix '-ability' (from Latin '-abilitas' via Old French) was attached to form 'appealability', and adding the prefix 'un-' produced 'unappealability'.

Initially, elements like 'appeal' meant 'to call upon or address (a higher authority)'; over time the derived formation came to denote the 'capacity to be appealed', and with the 'un-' prefix it evolved to mean 'not capable of being appealed' (current meaning).