The female origins of "stud" may come as a surprise to all the men out there who aspire to the term. While "studs" nowadays are virile and attractive in a masculine, athletic way, the word probably comes from the German word for "mare"--and the Middle English "stod," basically a place for breeding mares.
Hundreds of years later, the breeding definition still applies, but the gender has changed. Nowadays, a stud is a stallion, or a place where stallions are kept. Retiring racehorses are put "at stud" to be bred post-career, for example. (Mares can be put at stud, but they're never referred to as "studs.")
At some point in the early 20th century, "stud" was extended to male humans as well--especially the desirable ones with lots of sexual partners, but not always. Sometimes the sexual references were less overt, such as in the Beat lingo of 1950s, where a stud was just a "guy."
Just how sexual the term is and whether or not a stud is a sex object or a sexual aggressor is far from settled. Websites and magazines advertise men as studs to rent for money. But then there's the Michigan college student threatened with sexual harassment charges for using the term in a paper.
