Cerebellum comes from Latin meaning:

1. It sits behind and below the cerebrum. 2. Its name is a diminutive. 3. The cerebellum, from the Latin meaning little brain, accounts for about 10 percent of brain mass. 4. So the answer is little brain. _Source: OpenStax 'Anatomy and Physiology 2e', Ch 13 'Anatomy of the Nervous System'_