If I had to guess, I'd say "Hassel" is related to "Hasel" in this case (as is the case with quite a few similar place names), which would make it more like "David from the farm with the hazel trees" or something.

"Hassel" is German slang and translates to "hassle".

.. but that is new slang, and originates in "hassle" afaik. And I would rather say, it is just used (and written) as the original english word.

It could very well be exactly the other way around. Even my grandparents knew this word and taught it to my parents. It's absolutely not new.

Interesting, I never heard of it and will ask mine. Which area are you from? (maybe it is dialect?)

Anyway, I suppose most teens who use today, got the word from gangsta rap and their "street hassle" ..