Gallows Humor

 refers to an unmarked quest in Fallout 3.

The Betting Pool
Talk to some of the members of the Capital Wasteland Brotherhood of Steel Lyons' Pride Platoon in the Great Hall after gaining entry to the Citadel. They will tell you about a betting pool to try and guess Gallows's 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.

The Black Widow perk does not give you any extra options when talking to Gallows.

The ONLY way to find out his name is through the speech challenge, so save first and make sure your speech skill is high enough!

When talking to Gallows for the first time, if you should chose all 3 times it appears to have a better chance of working.

Reward

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

Reference
Possible reference to Saving Private Ryan. In the movie the soldiers in the squad which the movie is centered on, have a poll 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 thier own, to accomplish a mission.