Literally “journey-beer”. Usually a bottle or can of beer you have when leaving the pregaming location on your way to the main event / party. The form of commute is not important, walking, subway, bus - doesn’t matter. It’s your companion for the commute. Extra: it’s also called “Fußpils” which would mean “foot pilsner” - however it also sounds exactly like “athletes foot” in German which is a fun spin.