I have a character who starts as a low servant caste and rises up through society. While plotting, I never bothered to give her more than one name, I guess I was thinking her island/village is small enough that it wouldn't be important, and that she has no family name to claim. To be honest I didn't consider it in a "worldbuilding" sense, but the idea is also to signify she has no status of her own.
The rest of the characters come from societies modeled on Western culture, so they have first and last names, nicknames, and often ranks and titles.
My problem is coming up in dialog. I can signal the social hierarchy and also give hints to the mindset of the speaker though the way characters refer to one another: "Miss Karagi" vs "Joan Karagi" vs "Joan" vs "Lieutenant Karagi" – I can easily signify social hierarchy and levels of familiarity. It happens without even thinking about it.
This doesn't work on the character with one name, and now I'm stumbling over it again and again in dialog, especially since the way she is perceived by other characters is a major theme of the novel – some see her as a naive girl, some see her as a scheming social climber, etc. Her status also changes over time as she "levels up" in their society, and eventually she plays with these social perceptions, for example insisting on being called "Mrs Rothschild" (not the actual name) after only a tenuous relationship with a millionaire. She also eventually gains some infamy and at that point her one-word name works like Madonna or Cher.
But in the early stage, while she is still servant caste and only beginning her social climb, it's become a dialog issue because I've lost this level of subtlety. I'm not sure how to address her formally, and there is also a subplot about her name appearing on legal documents.
I'm not sure how to handle this as a writer, and I'm not sure how the characters themselves would handle it. How would (Westernized) characters refer to to this person with only one name? Would they give her a last name out of convenience (fix her, Ellis Island style) or are there other name conventions/euphemisms they would use? In casual dialog the people close to her would just use her name, but I don't know what to do when the dialog becomes formal, or people who aren't so personally familiar need to address her or talk about her. Are there ways I can signify these social layers and the personal perception of the speaker?