'anticoagulate' originates from the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'coagulate' (from Latin 'coagulare'), where 'coagulum' meant 'a clot' or 'curdled mass'.

'coagulate' comes from Latin 'coagulare' (to curdle, clot) and passed into English via Late Latin/Medieval Latin; the prefix 'anti-' was later attached in modern English/medical usage to form 'anticoagulate' and related derivatives such as 'anticoagulant' and 'anticoagulation'.

Initially 'coagulate' meant 'to cause to clot'; over time the compound 'anticoagulate' came to mean 'to prevent clotting' (i.e., acting against coagulation).