Eighteenth-century French physician Phillipe Pinel was among the first medical professionals to describe psychopathy, a condition that he referred to as maniaque sans delire, or "insanity without delirium." Other 19thcentury doctors recognized the affliction as well, describing it as "rational madness," "moral derangement," or "moral insanity." Then, in 1888, German psychiatrist J.L.A. Koch jumped in with a term of his own: psychopastiche, a German word meaning "suffering soul" — and the word "psychopathy" was born. It gained some clinical use in the early 1900s before the word "sociopathy" supplanted it in the 1930s, apparently to avoid confusion with another condition, psychosis. Sociopathy also suggested the influence of social and environmental factors in causing the disorder, which was a popular opinion at the time.
The current terminology emerged in 1980 when the Diagnostic and Statistical Manual of Mental Disorders (DSM), which lays out the standard terminology for they psychiatric profession, shed the term sociopathy in favor of the broader condition "antisocial personality disorder" (ASPD). Today, the descriptors "psychopath" and "sociopath" are still common and often used interchangeably because they denote the same personality traits.
But there is a difference, and it lies in the cause: Psychopaths present callous, unemotional tendencies because of physical abnormalities in the brain, while sociopaths show these same qualities as a result of social influences. Similarly, the terms "primary psychopath" and "secondary psychopath" denote this same physical/environmental divide. So when psychiatrists say "sociopath" or "secondary psychopath," they're essentially referring to the same thing [source: Hirstein].
Despite the publication of two new editions of the DSM since 1980, psychopathy is still relegated to the broader ASPD category. It's a sore point for many psychopathy specialists who are quick to point out that the two conditions are not the same, and, in fact, only 1 in 5 people with ASPD are psychopaths [source: Kiehl and Buckholtz].