hindmost segment of the brain, 1650s, from Latin medulla, literally "marrow," also "pith of plants," of unknown origin, perhaps related to or influenced by medius "middle" (but cf. also Old Irish smiur, Welsh mer "marrow"). The word was used in the Latin senses in Middle English. Related: Medular; medullary.
medulla me·dul·la (mĭ-dŭl'ə)
n. pl. me·dul·las or me·dul·lae (-dŭl'ē)
The inner core of certain organs or body structures, such as the marrow of bone. Also called medullary substance.
Plural medullas or medullae (mĭ-dŭl'ē)