When I moved to Kentucky at the age of twelve, I remember there being such a big shock to my system. No, it wasn't a different accent or slightly colder weather. It was first hearing someone offer me a "pop."
Was this some slang term for beating me up? No, they were offering me a coke. (Not Coke with the capital C, because it could have been a Coke or Pepsi, or heavens forbid, a RC). Never in my Georgian life had I heard the word "pop" to refer to the fizzy, calorie-laden carbonated beverage.
I think I assimilated by calling it pop moving forward, however I still find myself wanting to refer it to Coke. Occasionally I'll get confused at call it soda. Now, when in doubt I just offer people bourbon.
I noticed in this map of pop vs. soda, the state of Kentucky is divided. It seems like eastern Kentucky and Lexington are more likely to call it "pop," while Louisville and western kentucky call it "coke."
Perhaps it makes no difference at all, unless you forget your manners and fail to offer anyone a frosty bevvy. That, my friends, is just plain rude.
What do you call it?