I made a graph of my past relationships.

This joke cleverly plays on our understanding of basic geometry and the often-complex world of personal relationships. The humor mechanism here is pure wordplay, specifically a pun. When we hear "ex axis," our minds immediately jump to the "X-axis" found on any standard graph, but the comedic twist comes from connecting it to a former romantic partner, or "ex." Similarly, "why axis" is a phonetic twin of the "Y-axis," perfectly capturing the frequently asked, sometimes unanswerable, question of "why did it all end?" after a relationship concludes.

Graphs, with their familiar X and Y axes, are fundamental tools in mathematics and science, used to visually represent data and show relationships between different variables. This system, known as the Cartesian coordinate system, was famously developed by René Descartes, a French philosopher and mathematician. By applying this precise, logical framework to the inherently unpredictable and emotional landscape of past loves, the joke creates a delightful collision of concepts, turning a scientific visualization into a relatable, self-deprecating chuckle about love and loss. It's a testament to how language can be bent and twisted to find humor in even the most analytical of subjects.