I don't know if this matters or not but it is interesting to add this thought.

Given that a major scale is root, whole step, whole step, half step, whole step, whole step, whole step, half step (whole step), where you start is not relevant. Now, that does not address the math/physics question about where the standard 440hz tone tuning came from and who named that "A". If it was Bartolomeo Cristofori when he built that first piano in 1700, we can't ask him.... LOL!!

John brings up a funny story when mentioning the key that horns play in. When I started playing sax, I learned the horn in concert key. So when the sheet music says F#, and I play the F# fingering, I hear an A. Thus I learned that when I play that combination of keys depressed I get an A, and I moved forward calling that A. Made for some problems reading sheet music in college. I had to take every chart home and rewrite them in C so I could read them. LOL!!!