Sadism is a concept that is applied to rape-torture and rape-murder as well as the pleasures of consensual sadomasochism. From the 1890s, forensic psychiatrist Richard von Krafft-Ebing was responsible for popularising the term. This article explores Krafft-Ebing's understanding of the “degenerative” sadist and looks at how popular and psychiatric ideas changed over the past century. Why did it quickly become a common term in society? Why was sadism regarded as a “perversion” of “normal” male sexuality? In forensic terms, one interesting thing about the invention of sadism is why it needed to be coined in the first place. What was it about the sexual that necessitated a different category?