John Steinbeck's Of Mice and Men was published at a time (1937) in American history when the segregation of African Americans remained in full force. In Steinbeck's novel, most of the men who work on the barley farm sleep in the bunk house. The stable buck Crooks, however, has a separate room to himself and that room is attached to the barn. Crooks does not even sleep in the same sort of bunk as the other men, but rather "a long box filled with straw."
So segregated are the races that when Candy comes near to Crooks' room, Candy is "embarrassed" to enter it. Candy says that even though both he and Crooks have worked at the farm for a long time that "This's the first time I've ever been in his room."
Thus, when Candy talks to Crooks, he does so with a sort of embarrassed reverence.