OKAY maybe they have something to hide after all, circumstantially!!

Both know not to share their true name with fae or fairies, and Frieda is about to get slightly confrontational ("An ally wouldn't--"), but Neuvillette politely cuts her off before she gives away more than necessary. He explains that they'll swear on their names, but won't say them. Between his firm composure and Frieda's awakened mistrust, the fairy will have a hard time convincing them otherwise.