Often used as a synonym for margarine in the early 20th century, what four-letter word is a common name for the spread itself?

Oleo

Short for oleomargarine, the term 'oleo' comes from the Latin word for oil and the Greek word for pearl. In the early 20th century, U.S. dairy lobbyists successfully pushed for laws requiring oleo to be sold as unappetizing white blocks with a separate yellow dye packet to prevent it from being mistaken for real butter.