Why is a two year degree called associates?

The term "associate" in an associate's degree reflects the fact that the degree is associated with a bachelor's degree. It's a stepping stone, providing foundational knowledge and skills that often transfer to a four-year bachelor's program, allowing students to complete a bachelor's degree in less time than if they started from scratch. The associate's degree is thus *associated* with the higher degree, rather than being a terminal degree in itself.