Phrenology is a pseudo-scientific theory according to which from the conformation of the skull it is possible to trace the development of certain areas of the brain, the seat of particular psychic functions. The basis of this theory was worked out by the German physician Franz Joseph Gall (1758-1828).
In the first years of the 19th century this discipline became a social and salon practice. This fate was caused by a principle of phrenology which theorized that human instincts and talents having so many cerebral areas reserved for them, these areas constituted as many small brains, which manifested themselves on the external surface of the skull with visible and palpable protuberances or bumps, so much so that it was possible to recognize, by sight and touch, the intellectual and moral qualities of each individual. Hence the saying “have the bump for”, referring to a person with particular aptitudes towards a discipline.