Why is a college degree called a bachelor's degree?

The word "bachelor" comes originally from a Latin word "baccalarius," which is where the term "baccalaureate" comes from as well.

In Latin it originally meant a "vassal farmer." In the 1300s, a bachelor/baccalaureate came to mean a young knight or trainee soldier--because many young soldiers had been farmers and became soldiers looking for a different way of life. Over time, the meaning evolved some more, referring not just to a young solider but to any trainee, whether in a trade (guild) or at a university. (You can see also how the sense of "unmarried man" comes about, too--since young men are usually not married.) So the first degree that students earned at the university came to be called a "bachelor's degree" because it was the degree that young, novice students earned. (Later on, they could earn a "master's" degree once they became masters in their field, and later yet they could earn a "doctoral" degree; in Latin, "doctor" meant "highly educated.")