The term configuration management belongs to the general engineering vocabulary.
Its purpose is to keep record of the characteristics of all the parts/components of a complex system (e.g a car, a missile, an electronic device), and of course the change of these characteristics when a component is replaced with a similar component. A configuration describes exactly a specific product.
In other words, configuration management is version management for industrial products. It allows at any moment to assemble a previous version of a product.
In software there's no industry catalogue of parts that could allow to uniquely identify a piece of software and its successive versions and find it back in some warehouse to assemble (configure) an older version of the product. The software part/ component is best described by its code in its entirety. So configuration management for software means to manage the versions of the source code. This is why the term software configuration management is used for source code version management.
Note however that SCM is larger than only source code versioning. It may also include management of external dependencies (e.g. third party libraries or frameworks with versions managed somewhere else), external resources (e.g. third party binaries or dlls or API definitions to interoperate with external systems), as well as digital assets (e.g. pictures or videos to be packages with the end product).
