The origin of a muscle is the point at which it attaches to a bone (usually) or another muscle. The insertion of the muscle is the end of the muscle attaching to the freely moving bone of its joint. Muscle origin and insertion are terms that describe where the muscle attaches to the bones / connective tissues. They are relative. Generally, the origin is where the muscles originates on the body (usually a bone, but not always) of the stationary part. The insertion is where the muscle attaches on the bone of the moving lever across a single, or multiple, joint lines. When the muscle contracts, it pulls the insertion to the origin.