'fast-release' is a modern English compound formed from 'fast' and 'release'. 'fast' comes from Old English 'fæst' (originally meaning 'firm, fixed'), and 'release' comes via Middle English from Old French (e.g. 'releser') ultimately from Latin roots meaning 'to loosen/set free' (used in senses of letting go or relieving).

'fast' originally appeared in Old English as 'fæst' meaning 'firm, fixed' and over time developed additional senses including speed. 'Release' passed into Middle English from Old French (e.g. 'releser'), itself formed from Latin-derived elements meaning to loosen or set free. The compound 'fast-release' is a 20th-century coinage, common in technical and pharmaceutical contexts to describe formulations or mechanisms that release their contents quickly.

Initially, the components 'fast' and 'release' carried meanings of 'firm/secure' and 'set free/loosen' respectively; when compounded in modern usage the meaning has stabilized as 'to release quickly' (i.e., 'rapid release').