hydrogenous

Etymology tree
Proto-Indo-European *wed-
Proto-Indo-European *-r̥
Proto-Indo-European *wódr̥
Proto-Hellenic *údōr
Ancient Greek ῡ̆̔́δωρ (hū̆́dōr)
Ancient Greek ὑδρο- (hudro-)lbor.
French hydro-
Proto-Indo-European *ǵenh₁-
Proto-Indo-European *-os
Proto-Indo-European *ǵénh₁os
Proto-Hellenic *génos
Ancient Greek γένος (génos)
Proto-Indo-European *-os
Proto-Indo-European *-ēs
Ancient Greek -ης (-ēs)
Ancient Greek -γενής (-genḗs)lbor.
French -gène
French hydrogènebor.
English hydrogen
Proto-Indo-European *h₃ed-
Proto-Indo-European *-os
Proto-Indo-European *h₃édosder.?
Proto-Italic *-ōtsos or *-otsos
Latin -ōsus
Old French -usbor.
Middle English -ous
English -ous
English hydrogenous
From hydrogen + -ous.