'clot-preventing' is a modern compound of 'clot' + 'preventing'. 'clot' originates from Old English 'clott' meaning 'lump', and 'preventing' comes from the verb 'prevent', ultimately from Latin 'praevenire' (via Old French), where 'prae-' meant 'before' and 'venire' meant 'to come'.

'clot' developed from Old English 'clott' into the modern English 'clot'. 'Prevent' evolved from Latin 'praevenire' to Old French 'prevenir' and Middle English forms before becoming modern 'prevent'; the present participle 'preventing' is a standard English verbal adjective. The compound 'clot-preventing' arose in modern English usage, especially in medical contexts, by combining the noun and the participle.

Originally 'clott' meant 'a lump' and 'praevenire' meant 'to come before'; combined in modern usage they mean 'acting to stop the formation of (blood) lumps', i.e., preventing blood clots.