The old ideas where to spread a blanket and have a lunch box with sandwiches.
The more modern idea could be eating on tables and benches spread in local parks, and it can be just about any food save for barbecue (since that would be a barbecuer)
2- Dutch racist word to describe a nicker.
Pick (comes from the word Pik), stands for stealing
Nicker (comes from the english word nikker) stands for a black or colored person.
Black people are often seen as thieves in white societies.
2- He's a 'picknicker', because he's a nikker and he steals (hij 'pikt')