'antitetanolysin' originates from modern New Latin/English coinage, combining Greek prefix 'anti-' (meaning 'against') with 'tetanolysin' (from 'tetanus' < Greek 'tetanos' and Greek 'lysis' via the form 'lysin'), where 'anti-' meant 'against' and 'lysis/lysin' meant 'loosening' or 'destruction'.

'antitetanolysin' was formed in 20th-century medical/immunological English by compounding 'anti-' with 'tetanolysin' (a toxin name derived from 'tetanus' + '-lysin'); the modern English term developed directly from these scientific coinages without an intervening medieval form.

Initially it was a literal formation meaning 'against tetanolysin'; over time it came to be used as a technical noun referring specifically to an antibody or antitoxin that neutralizes tetanolysin.