Soda or Pop

When I ate lunch with my lab-mate, one of them called "Pop" to soft drinks. I call "Soda". It is so interesting thing for me. Then, I looked for interesting map in web site(http://gigazine.jp/img/2008/09/11/map_what_carbonated_beverage_called/popvssodamap.gif). Half of the area's people call "Pop". Uh... interesting!