Gallows Humor

 refers to an unmarked quest in Fallout 3.

The Betting Pool
Talk to some of the members of the Lyons' Pride in the Great Hall after gaining entry to the Citadel. They will tell you about a betting pool to try and guess Gallows' real name. You can ask Knight Captain Gallows about it after hearing about the bet. If your speech skill is high enough, you can convince Gallows to tell you his real name. After you find out his name you should speak to Paladin Glade, who is running the betting pool. Glade can be found near Gallows in the Great Hall in the A Ring area. Gallows tells you his real name is Irving and asks that he just be left alone.

Reward

 * The reward is the current betting pool, which has risen to 1000 Caps.

Behind the scenes

 * This may be a reference to Saving Private Ryan. In the movie, the soldiers in the squad which the movie is centered on have a pool over what their Captain's (Tom Hanks) career is back in America. Another similarity is that they also were sent away from a greater force, on their own, to accomplish a mission. One other similarity is that a member of the the captain's squad in Saving Private Ryan suggested that they wait until the pool reached $1000, the captain would give said member the answer and they would split the money.
 * Gallows humor is a type of humor that arises from stressful, traumatic, or life-threatening situations; often in circumstances such that death is perceived as impending and unavoidable. It is similar to dark comedy but differs in that it is made by the person affected.