'antiendotoxin' originates from Greek/Neo-Latin formation: the prefix 'anti-' (Greek 'anti' meaning 'against') combined with 'endotoxin' (from Greek 'endon' meaning 'within' + 'toxikon' meaning 'poison').

'endotoxin' entered scientific English from Neo-Latin/German usage based on Greek roots ('endon' + 'toxikon'); the compound 'antiendotoxin' was formed later by prefixing 'anti-' to 'endotoxin' in 20th-century biomedical terminology and became established in scientific usage as the term for agents that counteract endotoxin.

Initially the parts literally meant 'against' + 'within-poison' (i.e., 'against endotoxin'); over time this came to denote specifically an agent (antibody/serum/compound) that neutralizes endotoxin in medical and research contexts.