'autopoisonous' originates as a hybrid formation from Greek 'auto-' meaning 'self' and English 'poisonous' (from Old French 'poison', ultimately from Latin 'pōtiō/potionem'), where 'auto-' conveyed 'self' and 'poisonous' meant 'containing or producing poison'.

The prefix 'auto-' comes from Greek 'αὐτός' ('autos') meaning 'self'. 'Poisonous' developed in English from Old French 'poison' (from Latin 'pōtiō'/'potionem'), with the adjectival suffix '-ous' added in Middle English to form 'poisonous'. 'Autopoisonous' is a modern coinage combining these elements to form a technical adjective.

Initially the components meant 'self' and 'containing/producing poison'; over time the combined coinage has been used (rarely) to denote self-directed toxicity or the property of producing toxins that harm the organism itself, analogous to the established term 'autotoxic'.