Webster’s Revised Unabridged Dictionary · 1913
Fenian
Fe′ni·an, n. [From the Finians or Fenii, the old militia of Ireland, who were so called from Fin or Finn, Fionn, or Fingal, a popular hero of Irish traditional history.] A member of a secret organization, consisting mainly of Irishmen, having for its aim the overthrow of English rule in Ireland.
Fe′ni·an (fē′nĭ·an), a. Pertaining to Fenians or to Fenianism.