Rx is actually an abbreviation for a Latin word “recipere” that means “to take”

“Rx two aspirin” means to “take two aspirin”

That’s how it was initially used.

Also note its not that the symbol is not “R” and “x” next to each other like its believed to be

It’s a fusion, something like this:

Later Rx came to stand for “récipé” which means “prescription” and has hence been used as such.