The Etymology of Cortex
Cortex is, etymologically, bark — the outer layer of a tree that is stripped and discarded. Latin 'cortex' meant the bark of any tree, and the underlying Proto-Indo-European root '*(s)ker-' (to cut) is the same one behind English 'shear,' 'short,' and 'shard.' English borrowed 'cortex' as a technical anatomical term in the 1650s, originally for the outer layer of any organ — the renal cortex, the adrenal cortex. The cerebral cortex, now the most familiar sense, came into prominence with 19th-century neuroanatomy and 20th-century neuroscience. The same Latin word reaches English by another route as 'cork,' the bark of the cork oak, borrowed via Spanish. Cork in a wine bottle and cortex in a brain are the same idea: the rind that surrounds the substance.