Mid 17th century (in an earlier sense). As noun either an alteration (after nouns in -ac) of hegemonic, or perhaps from ancient Greek ἡγεμόνιος guiding, epithet of Hermes, guide of departed souls + -ac.
Definition of hegemoniac in US English:
hegemoniac
adjective
rare
Hegemonic.
Origin
Mid 17th century (in an earlier sense). As noun either an alteration (after nouns in -ac) of hegemonic, or perhaps from ancient Greek ἡγεμόνιος guiding, epithet of Hermes, guide of departed souls + -ac.