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In the book “You” by Caroline Kepnes, set in New York, the narrator “Joe” describes other characters this way:

“Your best friends are at the table next to mine, loud and disloyal, *real F-train types** with the boots and the overprocessed hair that quietly insults all the Jersey girls that do that shit on purpose.”*

I obviously don’t live in New York lol, so I was hoping someone could help me understand the “joke” or reference here?

Thank you in advance!

TLDR: Title.