During the middle of the 19th Century, a series of factors combined to create a new Irish patriotic movement. This organization was a revolutionary group dedicated to the overthrow of British rule in Ireland. It had its roots in both the United States and Ireland and was popularly known as The Fenian Movement, in honour of the Fianna, the ancient Irish warriors.
The origin of the term Fenian comes from Irish folklore. It described an ancient group of Knights who were self-reliant and had a passion for Irish land. So great was their passion according to the legend, they gave up a chance for world dominion to keep Ireland. This fit very closely with the beliefs of the modern movement and was taken as the organization name.
Times were hard for the Irish, and had been since England took control of the land. In the middle of the 1840's, however, things got much worse. The potato famine of 1845-1848 was a great disaster to the Irish population. In the space of three short years, the inhabitants of the country declined by over two million souls. Some of these two million people immigrated to America while most starved to death or died of disease.
After the famine ended, times remained very hard for the Irish. They never completely recovered from the disaster and many more Irish immigrated to America during the 1850's. Most of these people were of a very strong patriotic belief in their home country, and only left because they had to survive.