I’m currently reading Hunger by Norwegian author Knut Hamsun. Early on in the novel, the narrator encounters an anonymous woman in the street and creates a name for her:
I stand and gaze into her eyes, and hit, on the spur of the moment, on a name which I have never heard before–a name with a gliding, nervous sound–Ylajali!
When he later fantasizes about the woman, he calls her by this made-up name. (I’m not done with the book, so I don’t know if he ever discovers her real name.)