'anaphylactogen' originates from Greek, specifically the words 'anaphylaxis' (from 'ana-' meaning 'against' and 'phylaxis' meaning 'protection') and the suffix '-gen' meaning 'producer' or 'originator.'

'anaphylactogen' was formed in modern scientific English by combining 'anaphylaxis' and '-gen' to describe substances that induce anaphylactic reactions.

Initially, it meant 'a substance that produces anaphylaxis,' and this meaning has remained consistent in modern medical usage.