Hey ! I can't tell you for sure but i believe it's kind of a ghetto nickname for the area given by the people.
Most likely has something to do with dealing of psychotropics, and stating the obvious like any Lisbon ghetto and the whole country really is under "prohibition".
Specially cannabis and hashish are consumed by a large part of the population in Portugal.
Funny enough Jamaica and Portugal are many times associated with the consumption of Cannabis, BUT they are both decriminalized, not fully legalized, which brings problems and a werid environment with law enforcement.

I actually had tought in including a paragraph about this but didn't think it was relevant as it's part of our structural violence, and it was getting long.

Here is an article i wrote about decriminalization:
https://steemit.com/cannabis/@zedikaredirect/decriminalization-doesn-t-work-cannabis-in-portugal