How did we come to say something courteous to someone after they’ve sneezed

https://sh.itjust.works/post/4253316

How did we come to say something courteous to someone after they’ve sneezed - sh.itjust.works

How/why did saying things like bless you or gesundheit start? And when?

And why not farts
This guy I worked with used to say, “What happened?”. He would always feign concern for the farter.