'hydrogenous' originates from English, specifically the word 'hydrogen', where 'hydro-' meant 'water' and 'gen' (from Greek 'genes') meant 'producing', plus the English suffix '-ous' meaning 'full of' or 'having the nature of'.

'hydrogenous' developed in English by combining the modern scientific noun 'hydrogen' (coined in the late 18th century from French 'hydrogène', itself from Greek elements 'hydro-' + 'genes') with the adjective-forming suffix '-ous' to produce 'hydrogenous'.

Initially, the element name 'hydrogen' meant 'water-forming' (from Greek), and 'hydrogenous' originally meant 'produced by or containing hydrogen'; over time the term gained a specialized sense in geology/chemistry for materials formed by precipitation from seawater.