This might be an odd question, but how was the exponential function $e$ actually discovered?
We can easily say that $\pi$ was discovered when they(primitive people) divided the circumference of the circle by its diameter, but I'm unable to link any incidents like this to the origin of $e$.
Looking up on the internet I saw something about the calculation of interest rates linked to $e$, but I was unable to understand it, some explanation would be helpful.