If you know you know
I come not to bury this phrase but to praise it. I thought it was another content-free incoherence that could be mumbled in any context, like It is what it is, You already know, or that eighties classic, Whatever.
I was a fool.
Iykyk implies knowledge that only experience can bestow, that words can't fully describe, and that others without that experience can't fully comprehend. It communicates respect for that experience and offers a sense of connection with those who share it. The deep knowledge.
If you know you know.