Zouave was the title given to certain infantry regiments in the French army, normally serving in French North Africa between 1831 and 1962. The name was also adopted during the 19th century by units in other armies, especially volunteer regiments raised for service in the American Civil War. The 11th New York was initially led by Col. Elmer E. Ellsworth, until his death in 1861. The regiment was badly mauled during the First Battle of Bull Run in July 1861 as it acted as the rear guard for the retreating Army of the Potomac.
Benson John Lossing, ed. Harper's Encyclopedia of United States History (vol. 10) (New York, NY: Harper and Brothers, 1912)