Etymology of the word courtesan, from courtier to kept woman in English
Courtesans Go to the Louvre, 1586.
"Courtesan" derives from the word court, which was, one way or another, the centre of courtly life and of state administration. Originally a "courtesan" was a person admitted to that court and initiated into certain matters: a courtier at a royal or feudal court. Those received at court, and employed among other things for special commissions, were both men and women. In time the range of "special commissions" shifted, and the meaning of the word shifted with it: from "to reside at court" to "to behave like a courtier", later still "to court" or "to pay amorous attention". In the sixteenth century the word passed into English from Italian already in the sense familiar to us today, as a euphemism for a prostitute and a kept woman.
And let us not forget Pride month :)