derro - What does it mean?

Noun

I sat in the derros? park in Taylor Square. Knee-deep in drunks and drug addicts, it was called “Fantasy Island” by the cops.

He leaned back slightly, a small smile on his face. 'Who's gunna worry about an old derro' found dead in the gutter, eh? Sure, someone will find out who you once were, that won't cut any ice neither, you're a nothing now, less than a nobody, a drunken ' derro , a homeless person.'

“I was thinking of talking to the derro' again. He pointed the place out to me to begin with. Perhaps he knows more about it.”By ten-thirty I was down at Martin Plaza, but the ' derro wasn?t.