On Exes – Or at Least X’s

I know it’s a rando question, but: Why do so many abbreviations have X’s?

And these are just the ones I know, not even all the ones that are out there ….

Bx: biopsy
Dx: diagnosis
Fx: special effects
Px: physical exam
Rx: prescription
Sx: symptoms
Tx: treatment
Wx: weather