'serpin' originates from modern English as a coined acronym combining 'serine' and 'protease inhibitor' (SERine Protease INhibitor).

'serpin' was coined in the late 20th century to name a group of related proteins; it does not descend from older foreign-language roots but formed by abbreviation of descriptive English terms and then became the standard family name.

Initially, the term referred specifically to proteins that inhibit serine proteases; over time it broadened to denote a structurally related protein family with varied functions (some members have non inhibitory roles).