What is PEG in Dr Pepper?

Excuse me, could you please clarify what PEG stands for in the context of Dr Pepper? I'm curious to know if it's a specific ingredient, an abbreviation for a process used in the production, or perhaps something else entirely. I've seen it mentioned in relation to the beverage, but I'm not entirely sure what it refers to. Could you provide some insight into this matter? Thank you in advance for your assistance.