'asphyxiant' ultimately derives from Greek via Latin and French: from Greek 'asphyxía' (ἀσφυξία), where the prefix 'a-' meant 'not/without' and the root 'sphyx/ sphyxis' related to 'pulse' or 'throb' (loss of pulse associated with suffocation).

'asphyxiant' in English developed from French 'asphyxiant' (present participle/agent-form of 'asphyxier'), which came from Late Latin/Medieval Latin 'asphyxia' taken from Greek 'asphyxía'; this sequence produced the modern English form 'asphyxiant'.

Initially related to the Greek notion of 'absence of pulse' or 'lack of vital breath,' its meaning shifted in modern usage to refer specifically to agents or substances that cause suffocation or inhibit respiration.