Greek allos = other (than usual), and Latin cortex = bark, hence non-laminated external grey matter. It refers to paleo- or archi-cortex, as distinct from neocortex.

Gr. 'other cortex'. Phylogenically old, three-layered cortex in the temporal lobe ( Ch. 26).

The allocortex is a part of the cerebral cortex characterized by having fewer cell layers than the isocortex (less than six). The specific regions of the brain normally described as part of the allocortex are the olfactory cortex and the hippocampus. These two regions mediate olfaction and limbic input, respectively.