How did x and y become the primary letters used as variables in math?

Question

For cartesian plans, for functions, why are x and y the letters we use as variables?

In: 18

Answer 1

Algebra was bought to Europe by muslims when they invaded the Iberian peninsula. Back then, they called their unknowns “the thing”, witch in arabic is “say”. When traslated into latin form in Spain, it was written xei and, from there, x to name an unknown. Y, z to follow after x in modern alphabets.