English Etymology Etymology treeEnglish complexProto-Germanic *-in-Proto-Indo-European *-h₂Proto-Indo-European *-éh₂Proto-Indo-European *-yétiProto-Indo-European *-eh₂yétiProto-Indo-European *-h₂tiProto-Germanic *-ōnąProto-Germanic *-inōnąProto-Indo-European *-dyé-Proto-Germanic *-atjanąProto-Indo-European *-tusProto-Germanic *-þuzProto-Germanic *-assuzProto-Germanic *-inassuzProto-West Germanic *-nassīOld English -nesMiddle English -nesseEnglish -nessEnglish complexnessFrom complex + -ness. Noun complexness (uncountable) The state or quality of being complex.