Which part of a muscle is considered the more fixed attachment closest to the skeleton?

The part of a muscle that serves as the more fixed attachment closest to the skeleton is known as the origin. This term refers to the point where the muscle begins and is typically located proximal to the body's midline. In contrast to the muscle's insertion, which is the point of attachment that moves when the muscle contracts, the origin remains relatively stationary. Understanding this distinction is crucial for comprehending how muscles function during movement. By identifying the origin, one can determine the muscle's primary role in facilitating specific movements in coordination with associated bones and joints.