'hydrogen-poor' is a compound of 'hydrogen' and 'poor'; 'hydrogen' originates from Greek via French ('hydrogène'), from Greek elements 'hydro-' meaning 'water' and '-genes' meaning 'former/producer', and 'poor' derives from Old French 'povre' (from Latin 'pauper') meaning 'lacking/poor'.

'hydrogen' entered modern scientific English from French 'hydrogène' (late 18th century), itself coined from Greek roots 'hydro-' + 'genes'; 'poor' comes from Old French 'povre' and Middle English 'poor', and the compound 'hydrogen-poor' is a straightforward modern English formation combining the scientific noun with the adjective.

Initially 'hydrogen' literally meant 'water-forming' (reflecting the element's role in producing water in reactions), and 'poor' meant 'lacking'; combined in modern usage they mean 'lacking hydrogen' or 'having low hydrogen abundance'.