'antiknock' originates from the combining element 'anti-' from Greek, specifically the word 'anti' where 'anti-' meant 'against', and English 'knock' which comes from Old English 'cnocian'/'cnocc' where it meant 'to strike' or 'to hit'.

'antiknock' emerged in early 20th-century English as a compound in automotive and fuel-technology contexts (from the descriptive phrase 'anti-knock agent' for substances that prevent engine knock) and entered technical vocabulary as 'anti-knock' or 'antiknock'.

Initially it literally meant 'against (engine) knock'; over time it came to denote both the additives (agents) used to prevent knocking and the anti-knock property or resistance of fuels.