Echoes in the Dark

One character (DM’s discretion) always hears their name being called out whenever they are in, or near a cave. Other party members cannot hear it, and it sounds like someone whispering their name around the corner of the cave, or like a gentle beckoning into a cave
This could be worked in with one of their backstories - someone with ties to the Underdark feeling like they are being pulled/called into the Underdark, or back into it if they had previously escaped, or came from there.
This could be used as a storytelling device, leading them to something or leading them away from something.