Economic Inputs also called "Factors of Production"

In economics courses, we often talk about the inputs into the production process. I don't know why, but we call them "factors of production" when "inputs" seems just as good to me.

We lump the inputs into four categories: labour, capital, natural resources, and entrepreneurship. Of course there are varying subcategories of each, and we recognize that much labour can be thought of as "human capital" and that capital theory also helps us understand the utilization of natural resources. But trying to explain "entrepreneurship" is not always easy. 

Here's a great cartoon that might help:

There's some labour here, also some capital and some natural resources. But without innovative problem solving, those other things aren't worth nearly so much.