We do this stretch every night in my dojo, but I'm not entirely sure what it is called. I know that even if I could say it right, I cannot spell it. I think that what you are describing is what I would call "kata te" and then it sounds like you are saying "oh" and then like the word "sigh." Can anyone help me with the spelling?
The way that I would describe this stretch is that you hold your arm out, with your elbow down, hand pointing straight up, and your palm facing you. You grab your fingers and bring your hand (and forearm) down in a circular motion without moving your elbow much. It stretches out your fingers and the inside of your forearm.
I hope that this helps!