An insulting nickname for Pepsi. This works because if you rearrange the letters you get "penis," so you are comparing Pepsi to penis, or a gross penis I guess.
Deep in the heart of the south located in southern Alamance county there is a small town called snow camp. If you travel there you will heard the word "nepson" used frequently. This word is used to describe the inbreeding of brother and sister. The resulting offspring, if it lives, is called a nepson.