'peptide-forming' is a compound of 'peptide' and 'forming'. 'peptide' originates from Modern Latin 'peptidum', ultimately from Greek 'peptid-' (from 'peptein'), where the root 'pept-' meant 'to digest'. 'forming' comes from Latin 'formare' via Old French 'formant', where 'forma' meant 'shape' or 'form'.

'peptide' entered scientific usage from Modern Latin 'peptidum' in the late 19th / early 20th century and became English 'peptide'; 'form' passed into Middle English from Old French and Latin ('forma'), producing the present participle 'forming' used to indicate causing or producing.

Initially 'peptide' referred to digestion-related fragments (products of digestion), but over time it evolved to mean a short chain of amino acids linked by peptide bonds; 'form' originally emphasized shape ('forma') and later acquired the broader sense 'to make' or 'to cause', which is reflected in 'forming'.