sacrococcygealis
Sacrococcygealis refers to a small, variable muscle found in humans and other primates that attaches the sacrum to the coccyx. It is often considered part of the multifidus muscle group, which runs along the spine. The precise origin and insertion of the sacrococcygealis can vary, but it generally originates from the posterior surface of the sacrum and inserts onto the anterior or lateral surface of the coccyx.
This muscle plays a role in stabilizing the sacrococcygeal joint and may contribute to the slight movements