'antipestilential' originates from Modern English, specifically formed from the combining prefix 'anti-' and the adjective 'pestilential', where 'anti-' meant 'against' and 'pestilential' related to 'pestilence' (deadly epidemic disease).

'pestilential' derives from Middle English and Old French forms ultimately from Late Latin 'pestilentialis' and Latin 'pestilentia' meaning 'pestilence, plague'. The prefix 'anti-' comes via Greek 'anti-' ('against') into English; these elements were combined in English to form 'antipestilential' (attested in early modern and later English as a coined or literary term).

Initially it meant 'opposed to or preventing pestilence'; the core meaning has largely remained, though the word is now rare and often archaic or literary rather than common technical usage.