German slang term for the feast day 'Corpus Christi'.
The actual German translation is 'Fronleichnam', which sounds as if it would consist of the two words 'froh' and 'Leichnam' - They mean happy and corpse/cadaver.
A: Wohooo dude let's rock the bars from Wednesday to sunday!

B: We're supposed to work, I think.

A: You fail douche, thursday is Happy Kadaver - Movable feast!

A, B: YAY!
Get the Happy Kadaver mug.