Modern, non-religious circumcision began in the Victorian era as a means of deliberately desensitising and denuding the penis in order to discourage masturbation, which doctors then believed was the cause of insanity, epilepsy, hysteria, tuberculosis, short-sightedness, and death.
In 1891, Jonathan Hutchinson, president of the Royal College of Surgeons of England, in his article "On Circumcision as a Preventative of Masturbation," wrote:
Measures more radical than circumcision would, if public opinion permitted their adoption, be a true kindness to many patients of both sexes. [Jonathan Hutchinson. On Circumcision as Preventive of Masturbation. Archives of Surgery 1891;2:267-268]
The myth that circumcision improves hygiene originated at this time to mean the improvement of moral hygiene.
Clarence was addicted to the secret vice practised among boys. I performed circumcision. He needed the rightful punishment of cutting pains after his illicit pleasures.[N. Bergman. Report of a Few Cases of Circumcision. Journal of Orificial Surgery 1898;7:249-251.]
By the turn of the century, amputation of the foreskin was "scientifically proven" to cure and prevent malnutrition, paralysis, bed-wetting, hip-joint disease, headache, alcoholism, criminality, club-foot, and heart disease.
Even in the 1930s, some doctors openly declared in the British Medical Journal that sexual oppression of young men was their motivation.
Nature intends that the adult male shall copulate as often and as promiscuously as possible, and to that end covers the sensitive glans so that it shall be ever ready to receive stimuli. Civilization, on the contrary, requires chastity, and the glans of the circumcised rapidly assumes a leathery texture less sensitive than skin. Thus the adolescent has his attention drawn to his penis much less often. I am convinced that masturbation is much less common in the circumcised. [Cockshut RW. Circumcision (letter). Br Med J. 1935; 19 October: 764.]