hetaera (n.) Look up hetaera at Dictionary.com
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).