Postin'?

I am always amazed at what kids can come up with as their language. After working with high school students for three years, I can usually stay on top of the current 'lingo' for todays teens, but this seems to be a fleeting talent. Yesterday as I pop into work to check on a few things, a student greets me outside my office. He informs me that he has been "postin'" in my office. As I look on my desk for a post-it note, I realize something is not right. I look at him and ask "you were doing what in my office?" With a straight face, he replies, "Postin'". "Posting?" I ask.
"Posting? haha, No Mrs. Howard, it's Postin'." Then the light goes on. "You were hanging out in my office?" "Yes, I was postin'." "Postin' is the new hanging out?"
"Yes." "Where have I been?" He non-chalauntly says "well, Mrs. Howard, you have been gone for like half the school year." In all actuality, it was only three months and part of that was Christmas break, so how could I have missed this new word? I laughed pretty hard that afternoon about this misunderstanding. My student just laughed and shook his head as though "Postin'" has been a part of the English language for decades.