Cerebelum

The word [vermis] is Latin and means "worm". 

The vermis is the name given by Galen of Pergamon (129AD - 200AD) to the median lobe of the cerebellum, since when seen from the superior aspect, this cerebellar lobe looks like a multisegmented worm. See accompanying image, or click for a larger depiction. 

When seen in a median section,  the cerebellar vermis looks like a multilobulated leaf with the fourth ventricle of the brain at its base. It is composed of several smaller lobules: Lingula, central, culmen, clivus, tuber vermis, pyramid, uvula, and nodular lobes.

Median section image link courtesy of UCLA Radiology

Sources:
1. "The Origin of Medical Terms" Skinner, HA 1970 Hafner Publishing Co.
2. "Medical Meanings - A Glossary of Word Origins" Haubrich, WD. ACP Philadelphia
3 "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
4. "Anatomy of the Human Body" Henry Gray 1918. Philadelphia: Lea & Febiger
Image modified by CAA, Inc. Original image courtesy of bartleby.com