Etymology of the word 'Bershon'?

[toadbriar]

The word ‘bershon’ is new to me via a flickr.com photo group, which provides a pretty decent description of what it means:

Bershon is a word that I’m pretty sure is not really a word at all, but my friend Erin and I, growing up in two different cities, both encountered it separately in our youth. Both of us heard it used in exactly the same manner, namely the cool girls in middle school rolling their eyes and saying, “… and Kayla said yes, and I was like, ohmyGOD, whatever, I’m SO BERSHON.”

The spirit of bershon is pretty much how you feel when you’re 13 and your parents make you wear a Christmas sweatshirt and then pose for a family picture, and you could not possibly summon one more ounce of disgust, but you’re also way too cool to really even DEAL with it, so you just make this face like you smelled something bad and sort of roll your eyes and seethe in a put-out manner.

It’s great to have a word for that! While discussing her recent visit with my 13 year old neice, my mom described this state perfectly and to my delight, she is familiar with the term. But she’s not sure HOW she knows of it - she is pretty sure she didn’t grow up using it. How old is the word ‘bershon’ and where does it come from?