What is Poepen?
1.
It mean 'to shit' in Dutch. And NOT 'wanna fuck?' as stated in a previous statement.
Ik moet poepen. -- I need to take a shit.
See
2.
Dutch (Antwerp dialect) for 'to fuck'. Most likely derived from 'poep' which is Dutch for ass. As in getting your ass naked and get it on.
"Hey schat, poepen?" English translation: "Hey love, wanna fuck?"
See