Do you know ghouls from goblins and ghosts?
1820, "mistress," from Medieval Latin hetaera, from Greek hetaira "female companion," in Athens opposed to "lawful wife," and thus embracing everything from "concubine" to "courtesan;" fem. of hetairos "comrade, companion," from PIE *swet-aro-, suffixed form of root *s(w)e- (see idiom).
(Female Companion), one of a class of professional independent courtesans of ancient Greece who, besides developing physical beauty, cultivated their minds and talents to a degree far beyond that allowed to the average Attic woman. Usually living fashionably alone, or sometimes two or three together, the hetaerae enjoyed an enviable and respected position of wealth and were protected and taxed by the state. Though they were generally foreigners, slaves, or freedwomen, their freedom was greater than that of the married woman, who was bound to seclusion. That their homes were frequented by married men was not censured by society. They were often hired as entertainers for symposia and family sacrifices. The hetaerae of Corinth and Athens were especially noted for their outstanding physical and cultural accomplishments. Phryne and Lais are historic representatives