Fenian

Partly from both of the following: * from Old Irish Féni (“originally the legendary people who inhabited Ireland; later the Irish people generally, especially those belonging to the social class of free citizens”, plural); further etymology uncertain, possibly ultimately from Proto-Indo-European *weǵʰ- (“to bring; to transport”) (whence wagon and wain; referring to the use of chariots); and * from Irish fian, fiann (“roving band of (legendary) warrior-hunters”) (generally a view taken by English-speaking scholars, possibly due to the similarity between Old Irish Féni and Irish féine, féinne, the genitive singular forms of fian and fiann), from Old Irish fían, ultimately from Proto-Indo-European *weyh₁- (“to chase, pursue”); + English -ian (suffix forming adjectives with the sense ‘from; related to’; and forming nouns with the sense ‘one from or related to’). The adjective is attested slightly earlier than the noun.