In Greek mythology, nymphs were beautiful beings associated with specific elements of nature. There were wood nymphs and water nymphs and nymphs who protected certain trees, meadows or mountains.
But just how did the term nympho (short for nymphomaniac), used to describe a woman with an overactive or uncontrollable sex drive, come to derive from the name for these mythical creatures?
The Greek word νυμφη, or nymphe, has multiple meanings including "bride" and "veiled." Hence, nymphs, in addition to being beautiful and eternally youthful (though not necessarily immortal), were "marriageable" creatures. Descended from gods, it's no surprise that unions with a nymph were particularly auspicious, and resulted in the birth of kings and heroes. (Ever heard of Achilles? Well he was the son of King Peleus and Thetis, a water nymph.)
Unlike their contemporary counterparts, however, nymphs are often depicted as chaste, spiritual beings who fall victim to the obsessive sex drives of some Greek god or satyr. Such was the case with Daphne, the sun god Apollo's first love, who prayed to Zeus to save her from being ravished and was transformed into a tree.
In 1775 the French doctor M.D.T. Bienville transformed the meaning of the word nymph forever by combining it with mania (Latin for madness or insanity) to form the word nymphomania. He used it to describe a "female disease characterized by morbid and uncontrollable sexual desire."
The slang term nympho first appeared in 1935 and its meaning remained pretty much the same. Today the term is still reserved for women who, according to urbandictionary.com, "eat, breathe and live for sex." But just because a woman is interested in sex (or in the case of nymphos, extremely interested), doesn't make her slutty or whorish despite the connotations the term often carries.
After all, the nymphs of ancient Greece usually got involved with one lover or no lover at all. And just because a woman's interested in sex doesn't necessarily mean she's interested in having it with anyone and everyone she meets.