Scotch doubles

"Scotch doubles" - In pool/billiard terms this means a doubles match in which team mates "share" an inning by playing alternate shots... But what is the origin of the phrase?

Thanks in advance for any help you can provide with this conundrum... This is a question that appears on pool web sites like mine almost every year!

My guess would be that it's a pejorative use of the term scotch to imply "cheap" since 2 players only pay for one game. I've also seen it used in bowling.