Fenian is a term used since the 1860s for an Irishnationalist who espouses violence, usually by people opposed to their aims. It can also specifically refer to the Fenian Brotherhood.
In 1865-66, following the US Civil War, Irish-Americans who were former soldiers of the Union Army launched raids into British North American territory in the Province of Canada in order to put pressure on the United Kingdom to leave Ireland. These were known as the Fenian Raids.
External links
1865 Newspaper Article Describing the Fenians (http://www.sonofthesouth.net/leefoundation/civil-war/1865/the-fenians.htm)
Fenian is also the name of the horse that won the Belmont Stakes in 1869. His image appears atop the trophy awarded to the winner of the Belmont Stakes.
The Fenian cycle is made up of stories about the Fenians (or Fianna), warrior-bands of Old Ireland, centers around the famous "Finn" of Finn Mac Cumhail.
The Fenians were so skilled in the magical arts of poetry and fighting that they seem to have been a combination of warriors and Druids, with the Druidic freedom to move from one tribal territory to another.
Another Fenian story, late in the tradition, is called Oisín in Tir na nÓg, and is about Finn Mac Cumhails son Oisín (Usheen) ("little deer"), who was invited and brought to the Otherworld.