also demimonde, "women of equivocal reputation and standing in society," 1855, from French demi-monde "so-so society," literally "half-world," from demi- "half" + monde, from Latin mundus "world" (see mundane).
Popularized by its use as title of a comedy by Alexandre Dumas fils (1824-1895). Dumas' Demi-Monde "is the link between good and bad society ... the world of compromised women, a social limbo, the inmates of which ... are perpetually struggling to emerge into the paradise of honest and respectable ladies" ["Fraser's Magazine," 1855]. Thus not properly used of courtesans, etc.
Compare 18th-century English demi-rep (1749, the second element short for reputation), defined as "a woman that intrigues with every man she likes, under the name and appearance of virtue ... in short, whom every body knows to be what no body calls her" [Fielding].