Unfortunately, Sam is the fullest name that readers are given for Sam in this story. Sam is the narrator of the story, and he doesn't provide readers with his full name; however, he does provide readers with his partner's full name. His partner is Bill Driscoll, and Bill only uses Sam's first name throughout the entire story.
Sam and Bill are kidnappers, and they are incapable of controlling little Johnny Dorset. They are basically bumbling fools; however, they are smart enough to not sign their names in any way to the ransom letter that they give to Ebenezer Dorset. Instead, they sign their letter "Two Desperate Men." It's a great signature because it must sound slightly threatening; however, readers know by this point that Sam and Bill are just desperate to be rid of the kid. The only other name for Sam is "Snake Eye, the Spy." This is the name that Johnny Dorset gives Sam for his various games and antics that he puts the two kidnappers through.
Sam is one of the two kidnappers in the O. Henry short story, "The Ransom of Red Chief." Sam and his partner, Bill, decide to abduct the son of a wealthy Summit, Alabama man, Ebenezer Dorset. But little Johnny Dorset makes life miserable for the two men. To entertain him, they play a running game of cowboys and Indians, of which Johnny goes by the name of "Red Chief." Bill Driscoll, one of the kidnappers, allows himself to be called "Old Hank, the trapper, Red Chief's captive," who is supposed to be scalped at daybreak. Sam, the narrator of the story, whose last name is never revealed, is called "Snake-eye, the Spy" by the young terror, Red Chief.