I have an observation regarding the the scoreboard. Each player/pair's score has a seperate 'marker' on the board. When it is 30 all - both markers will be 30 - so it might have been referred to as ' 30's are up' which in turn may have been shortened to '30 up' over time.
I tried looking for a glossary of the terms used by the scorekeeper - but couldn't find one.
Other sport's scorekeepers came up in the search. Baseball was one, and as the question refers to an American club I would not be surprised if this term migrated from one of the commonly played games in the States.
The only example I can give is that certain sporting terminology has become part of our language.
https://en.wikipedia.org/wiki/List_of_sports_idioms As you seem to want things referenced I put that in as a bookmark until I can find something more appropriate. It was an easy option to show that words migrate. For the subject of the enquiry I think I would need a more sport related example:- poor example - the use of 'advantage' during coverage of penalty shoot outs. I'll have to come back to this over the weekend.