'anti-clotting' is formed from the Greek prefix 'anti-' meaning 'against', the English noun 'clot' (from Old English 'clott' meaning 'lump'), and the verbal/gerund suffix '-ing' indicating action or process.

'clot' descends from Old English 'clott' meaning 'lump'; over time it became Middle English 'clot' and then modern English 'clot'. The productive Greek prefix 'anti-' (from 'anti') was combined with 'clot' plus '-ing' in modern English to form the compound 'anti-clotting'.

Originally the elements meant 'against' (anti-) and 'lump' (clot); in medical usage the compound evolved to mean specifically 'acting against blood coagulation' rather than a general 'against lumps' sense.