Read up on Shibboleth [1]. Using language or phrasing, it's a way to suss out members of a certain group. One can argue that the internet memes are a type of shibboleth for internet groups. One example is The Narwhal Bacons at Midnight [2]. I'm sure YC alumni have some type of shibboleth to identify themselves in situations.

Shibboleth entered mainstream culture (and when I learned it) via a West Wing episode called "Shibboleth" [3]. The clip is worth a watch.

[1] https://en.wikipedia.org/wiki/Shibboleth

[2] http://knowyourmeme.com/memes/the-narwhal-bacons-at-midnight

[3] https://www.youtube.com/watch?v=fqkaBEWPH18

To an extent I can describe it the concept would be "jargon" on a broad level.

https://en.wikipedia.org/wiki/Jargon

Thus, certain groups engage in trying to build up minor tests or cues to test a person's depth or familiarity with a professional subject. So if I'm talking to a person at a bar, and I find out they work at a major bank, say, Comerica, I can probe enough, politely, to probably understand what they do. This level of professional knowledge is not easily faked - it's like a web of synaptic references tagged to various terms and concepts (mostly "made up" for an industry).