I think I’ve been calling them “Vinn Diagrams” incorrectly all this time, so I’ve never attributed them to John Venn.
John Venn popularized the diagram we associate with his name, but he did not invent it. It was likely used at least a century before him, and probably long before that by anyone with a stick, a plan, and some dirt. And he most certainly didn’t call them “Venn diagrams” while he was alive, which would have been a pretty egotistical thing to do.
“You know what would explain this? A ‘Me’ diagram.”
They are related to a way of describing data sets called Euler diagrams, who are named after a guy named Euler who probably didn’t call them “Euler diagrams”. John Venn actually called his “Euler circles”. Each of these diagrams have a simple definition: A set of closed curves drawn in a plane (like on paper) whose spatial representation shows you how their data relate. They are a stunningly simple way to explain logical relationships using geometry, actually.
If the circles are too hard for you to draw, you could always opt for the five-ellipse version:
And who says that freehand circles are impossible to sketch? There’s a whole world championship for that, featuring guys like this: