There are many nicknames in Texas Holdem Poker. For example a pair of aces is called "pocket rockets". The nickname "Pocket Hitler" means you have a pair of eights as a starting hand. The 8th letter of the german alphabet is "H" and two times the 8th letter is "HH" wich was used in the Third Empire to shorten the "Heil Hitler" salutation.
A pokerplayer: "Holy shit, I went all in with a Pocket Hitler and had to wait until the river showed me another eight!"
Another pokerplayer: "You lucky basterd. I started with a pair of kings and thats all I got!"