'proteinless' originates from Modern English, specifically from the compound of 'protein' and the suffix '-less', where 'protein' comes from Neo-Latin/Greek roots referring to the primary substance and '-less' (from Old English) meant 'without'.

'protein' was coined in the 19th century (credited to J. Mulder, 1838) from Greek 'proteios'/'protos' meaning 'first' via Neo-Latin 'proteina'; the suffix '-less' comes from Old English 'lēas' meaning 'free from' or 'without'. These elements combined in Modern English to form 'proteinless'.

Initially the components referred to 'protein' (the principal substance) and '-less' ('without'); over time the compound came to mean simply 'without protein' in modern usage.