A homunculus is a small human being. Popularized in sixteenth-century alchemy and nineteenth-century fiction, it has historically referred to the creation of a miniature, fully formed human. The concept has roots in preformationism as well as earlier folklore and alchemic traditions.
Paracelsus is credited with the first mention of the homunculus in De homunculis (c. 1529–1532), and De natura rerum (1537).
19th-century engraving of Wagner and Homunculus from Goethe's Faust II
A cortical homunculus is a distorted representation of the human body, based on a neurological "map" of the areas and proportions of the human brain dedicated to processing motor functions, and/ or sensory functions, for different parts of the body. Nerve fibres—conducting somatosensory information from all over the body—terminate in various areas of the parietal lobe in the cerebral cortex, forming a representational map of the body.
3-D sensory and motor homunculus models at the Natural History Museum, London
Image: Rear of Sensory Homunculus