'nonappealable' originates in English as a combination of the negative prefix 'non-' (from Latin 'non', meaning 'not') and the adjective 'appealable' (from 'appeal' + '-able'). 'Appeal' comes ultimately from Old French and Latin roots.

'appeal' came into English from Old French 'apeler'/'apel' (to call), ultimately from Latin 'appellāre' (to address or call upon). The adjective 'appealable' was formed in English by adding the suffix '-able' to 'appeal'; 'non-' was later prefixed to create 'nonappealable'.

Originally 'appeal' in Latin meant 'to call upon' or 'to address'; over time in English it acquired the legal sense 'to apply to a higher court for review'. 'Nonappealable' now specifically means 'not able to be appealed' in that legal sense.