1560s, from Latin cerebellum "a small brain," diminutive of cerebrum "brain" (see cerebral).
cerebellum cer·e·bel·lum (sěr'ə-běl'əm)
n. pl. cer·e·bel·lums or cer·e·bel·la (-běl'ə)
The trilobed structure of the brain, lying posterior to the pons and medulla oblongata and inferior to the occipital lobes of the cerebral hemispheres, responsible for the regulation and coordination of complex voluntary muscular movement and the maintenance of posture and balance.