Well I just thought it was John! Well Jonathan. Did it drive your mom crazy for people to call you jonny or did she call you jonny? My mom insisted on Jonathan for my brother, but we still called him jon. Of course I called him brat but that's a different story. :)
It was the other way around for me--I insisted on being called Jonathan when I was a kid and a teenager. My mom called (and still calls) me Jonny. My dady calls me by a nickname which I will not divulge :)
I dropped "Jonathan" for myself a long time ago--mainly because people kept misspelling it!