Good In Bed

I am just finishing "Good In Bed" and I found so many good lines I wanted to steal from it.
If you haven't already read it, it's worth the $13. I really liked how she turned Minnie Driver into a fictional character named Maxy. Nice touch.
There was a section where I read a very familiar term, "Yay me."
When did that term sprout up? I was taught as a child that "yay" was spelled "yea."
I first noticed Kelly over at 'Welcome to my Life' using it. Now it seems I see that term wherever I go.
I have even been tempted to use it, though I think it's age inappropriate, kind of like when my daddy started saying "groovy" in the 70's and looking like a jackass.
I am a linguistic sponge, and I have to be vigilant not to use too much collegiate slang, lest I seem like one of those geezers who refuse to accept their age.
So yay me, for being, like, totally aware of how I use the language. I am all about that!