'peptide-free' is a recent English compound formed from 'peptide' + 'free'. 'Peptide' originates from Modern New Latin/Neo-classical formation from Greek 'peptein' (to digest) via form 'pept-' meaning 'digested' or 'having been digested', while 'free' originates from Old English 'frēo' meaning 'not in bondage, exempt'.

'peptide' was coined in scientific Latin/modern chemistry in the 19th–20th century from Greek roots related to digestion (compare 'peptid-' in biochemistry), and compounds combining a noun with 'free' (e.g. 'sugar-free') have long been productive in English; 'peptide-free' follows this pattern as a modern compound adjective used in labels and technical descriptions.

Initially the elements referred to 'digested' (Greek root) and 'not bound' (Old English); over time 'peptide' became the technical term for short chains of amino acids and 'free' became the adjectival suffix meaning 'without X', so 'peptide-free' now means 'without peptides' in technical and commercial contexts.