'amino-acid' originates from New Latin/chemical nomenclature, specifically the combining element 'amino-' (from 'amine') and the English word 'acid', where 'amine' ultimately traces to 'ammonia' and 'acid' comes from Latin 'acidus' meaning 'sour'.

'amino-acid' changed from the mid-19th-century coinage 'amine' (coined to name derivatives of ammonia) combined with the word 'acid' in the late 19th century to name compounds bearing both amino and carboxyl groups; it became established in biochemical vocabulary to denote protein constituents.

Initially, it meant a chemical compound bearing both an amino and an acidic group; over time it evolved into the specific biological sense of 'the building blocks of proteins' and the catalog of standard amino acids and their nutritional/biological roles.