'antidiphtheria' originates from the combining form 'anti-' from Greek and 'diphtheria', ultimately from Greek 'diphthera' meaning 'leather'; the term is a New Latin/medical formation meaning 'against diphtheria'.

'antidiphtheria' developed in 19th-century medical English as a formation combining 'anti-' + 'diphtheria' (it is related to earlier adjectives like 'antidiphtheric'); 'diphtheria' entered English via New Latin from Greek 'diphthera'.

Initially coined to convey opposition to the disease characterized by a leather-like membrane, it has retained the sense 'acting against diphtheria' and is now applied to serums, antitoxins, and vaccines.