it's a... thing

it's a (type of person) thing

Something is only understood or appreciated by a certain type of person or group of people. I know it seems like they're really insulting each other, but they're actually being really friendly. Banter like that is just an Irish thing, I guess. I can't help but stop at every bridge I cross and examine the workmanship. It's an engineer thing.
See also: of, thing
Farlex Dictionary of Idioms.

it’s a... thing

(informal) it is something that only a particular group understands: You wouldn’t understand the attraction of fast cars — it’s a man thing.
See also: thing
Farlex Partner Idioms Dictionary
See also:
  • it's a (type of person) thing
  • big with
  • big with (someone)
  • big with someone
  • be ahead of (someone's or something's) time
  • be ahead of/before/in advance of your time
  • it's an ill bird that fouls its own nest
  • trash talk
  • not be lost on (someone)
  • not stand for (something)