The term Oleo in Baking

I found a recipe for Chicken Pot pie that I am going to try and in the recipe for the crust it calls for Oleo. I wasn't sure if it was butter, margarine, or shortening since I know all of those can be used for crust. Upon resaerching the internet I have found that it is a name brand of margarine. I also read in several places that it is a Southern term and then also read it was a Northern term. So anyway Oleo is margarine.