What's a "ya-ya?"

Someone asked me what that means... my grandbabies (and now my husband and nearly everyone in my family) call me that. It is actually the Greek name for grandmother (although we are not of Greek descent). When my son informed me that I was going to be a grandma, he stopped and said, "ooooh that sounds funny." And we began searching for the perfect "grandma" name for me. Everyone thinks it fits me, so there you go.