'nonextensibility' originates from Modern English, formed by the negative prefix 'non-' and the noun 'extensibility'; 'non-' ultimately comes from Latin 'non' (meaning 'not'), and 'extensibility' derives from Latin components related to 'extendere'/'extensibilis', where 'ex-' meant 'out' and 'tendere' meant 'to stretch'.

'extensibility' developed from Latin 'extensibilis' via Late Latin and Medieval Latin into Middle English forms (e.g. Old French/Medieval Latin influences) and became the English 'extensibility'; 'nonextensibility' is a later productive formation by prefixing 'non-' to that noun.

Initially the roots conveyed 'out' + 'to stretch'; the modern combined term has the straightforward negative meaning 'the state of not being capable of extension'.