system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are the letters x, y and z used for representing points in a coordinate system?
gpt
Rene Descartes started using those letters to represent unknown coordinates in his maths book 'La Geometrie' and everybody else followed the convention from there. Same reason as that the ratio between circumference and diameter uses the π symbol - Euler started doing it and it got popular from there.