It was just a deragatory term used to describe the old world mobsters who were seen as outdated unaware of the many opportunities that were in america. I think the mustache thing is a contrast where scicly=mustaches and america=clean shaven.

"Let me tell you something. There's no nobility in poverty. I've been a poor man, and I've been a rich man. And I choose rich every fucking time."

-Jordan Belfort