The word "degree" in the context of academic achievement has its roots in the Latin word "gradus," meaning "step" or "stage." Medieval universities, particularly in Bologna and Paris, used a system of steps or stages in their educational programs. Gradually, these steps became associated with specific levels of accomplishment, culminating in the award of a diploma or certificate, which we now associate with a "degree."
So, while there's not a single, definitive origin point like a specific person or document, the concept evolved organically from the hierarchical structure of learning within medieval universities, with the Latin "gradus" providing the linguistic foundation.