'amino-acid-synthesizing' is a compound formed from 'amino acid' + the present-participle form of 'synthesize'. 'amino' ultimately comes from 'amine' (coined in 19th-century chemistry from French 'amine' and relating to 'ammonia'), 'acid' comes from Latin 'acidus' meaning 'sour', and 'synthesize' derives from Greek 'synthesis' (σύνθεσις) composed of 'syn-' 'with/together' + 'tithenai' 'to put/place'.

'synthesize' comes from Greek 'synthesis' (σύνθεσις) → Late Latin/New Latin technical use in chemistry → English verb 'synthesize' coined in the 19th century as chemistry vocabulary. 'amino' comes from 'amine' (term introduced c.1830s in organic chemistry) and was combined with 'acid' to form 'amino acid' in biochemical nomenclature; the compound adjective 'amino-acid-synthesizing' is a modern formation combining that noun with a verbal -ing form.

Originally, Greek 'synthesis' meant 'a putting together' or 'composition'; over time it became a technical term in chemistry for producing a compound from simpler substances, and in modern English 'synthesize' broadly means 'to produce or combine parts into a whole', with 'amino-acid-synthesizing' specifically meaning 'producing amino acids'.