'ATIII' originates from English, specifically the word 'antithrombin' combined with the Roman numeral 'III', where 'anti-' meant 'against' and 'thrombin' referred to the enzyme 'thrombin'.

'antithrombin' developed as a modern biomedical term from 'thrombin' (from Greek 'thrombos' meaning 'clot') with the prefix 'anti-' to indicate inhibition; the designation 'III' was later appended to distinguish isoforms, producing the abbreviated form 'ATIII'.

Initially the components referred generally to an inhibitor of thrombin; over time the term evolved into a specific protein designation ('antithrombin III') and the abbreviation 'ATIII' came to refer to that specific anticoagulant protein.