IPA: /haɪˈdrɒdʒənəs/
KK: /haɪˈdrɒdʒənəs/
Relating to or containing hydrogen.
Water is a hydrogenous compound made up of hydrogen and oxygen.
Hydrogenous → It is formed from "hydro-" (from Greek "hydor", meaning water) and "-genous" (from Greek "genes", meaning born of or produced by). The word "hydrogenous" refers to something that is produced from or related to water.
Think of 'water' ('hydro-') being 'produced by' ('-genous') — that's why hydrogenous relates to something that comes from water.