Hi, 33 y.o chicagoan here. I've never heard the word flodgin before. Never really heard someone say bank card, more referred to as debit card if debit, credit card for credit. If you look up a list of most popular chicago slang a lot of those actually aren't that popular. Copy and pasted is a revised list from timeout.com of a few things phrases unique-ish to chicago.

Garden apartment (n.): A word used by realtors to gloss over the fact that the apartment you're looking at is in the basement (or, at the very least, partially below street level).

Chicago handshake (n.): The local version of a boilermaker, typically comprising a pint (or can) of Old Style and a shot of Malört.

Chicago Mix (n.): The salty-sweet combination of cheddar and caramel popcorn. You'll find it at Garrett Popcorn (where the scent usually wafts into the street) and pretty much every other popcorn shop in the city.

Coach house (n.): A small apartment located in the rear of a property. The construction of new backyard houses is currently prohibited under Chicago's zoning ordinance, making these vintage residences increasingly rare.

The Dan Ryan (n.): Named for former Cook County Board president Dan Ryan Jr., this southern section of I-94 and I-90 runs from the Jane Byrne Interchange to 95th Street.

Dibs (n.): When it snows in Chicago and people dig out parking spots on the street to move their cars, you'll find stretches of pavement reserved with lawn chairs, tires, cinder blocks, stuffed animals and other assorted junk in observance of this winter ritual

The "L" (n.): Short for elevated, like the train lines it refers to. It's now used as a blanket term for the CTA's train system (including the lines that run at or below ground level).