'protein-poor' originates from the combination of 'protein' and 'poor', where 'protein' refers to essential nutrients and 'poor' indicates a lack or deficiency.

'protein' comes from the Greek word 'proteios', meaning 'primary' or 'first', and 'poor' from Old English 'pōr', meaning 'lacking'.

Initially, 'protein-poor' simply described a lack of protein, and this meaning has remained consistent.