On Deck or In the Wings?

It came to my attention whilst I was writing my last blog post that Scott and I use different terminology for something that's "coming up." Writing about 2020 and what was next for us, I mentioned that we had several clients that were waiting to schedule their sessions and I was keeping their dates on hold for deposits. I said "She's in the wings." Then Scott said, "Which client is on deck?" Which do you use? My guess is that it depends on whether your formative years were engaged in music and stage or in sports terminology. What if you were brought up with both? Does "In the Wings" mean something different than "On Deck?" Thats it. Just wondering what everyone else thinks.