Armpit

The sensitive boy

 Armpit, is a character in the novel Holes by Louis Sachar. He is an inmate at Camp Green Lake and a member of Group D. His real first name is Theodore. Like with most of the other characters, we do not know why Armpit was sent to camp Green Lake. He is the highest ranked in Group D after X-Ray, the tallest after Stanley, and the fastest digger after Zero. Just like X-Ray and Zero, he is dark-skinned. 

Armpit, just like the other boys, does "whatever X-Ray asked" (Part 1, 43%). His nickname was probably assigned to him by X-Ray, and although Stanley also has no idea "why anyone would want to be called Armpit" (Part 1, 15%), Armpit insists on being addressed only by that name. When Stanley calls him by his real name on his first day...