What is "nuckledu"

Du Dang, more commonly known by his nickname NuckleDu, is an American fighting game player known for playing Guile and Decapre in Ultra Street Fighter IV, Guile and Zangief in Street Fighter X Tekken, and Nash in Street Fighter V. NuckleDu was ranked as the 13th best player in Ultra Street Fighter IV by Eventhubs, who was ranked at #19 in the previous year and #32 in 2013.