The illegal club in the novel where Handmaids are used as prostitutes is called Jezebel's. The Commander presents it as a private club for senior Gilead officials, their guests, and visiting trade delegations, but it functions as a state-tolerated brothel.
The women working there are called Jezebels. Many are educated or considered unsuitable for the Handmaid system, and the regime has them sterilized so they cannot bear children. They are allowed make-up, alcohol, and revealing costumes from the pre-Gilead era, privileges denied to most women.
The name refers to Jezebel, the biblical queen associated in Gilead's ideology with sexual immorality and religious corruption. That naming is deliberately hypocritical: powerful men use the club while the women receive the condemnation.
Offred visits Jezebel's with the Commander and unexpectedly finds her friend Moira there. Readers sometimes confuse the club with Mayday, but Mayday is the resistance network, while Jezebel's is an institution controlled by Gilead's elite.