More from David Markson’s interview at the Dalkey Archive:
DM: Originally I was calling it “Wittgenstein’s Niece.” Never knowing, of course, that Thomas Bernhard would eventually publish something called “Wittgenstein’s Nephew.” But even before I submitted it I knew I’d have enough trouble finding a publisher as was—hardly the amount I did have, but some—and so not wanting to compound the difficulty I changed it to “Keeper of the Ghosts.” Which is something I swiped from Lowry, by the way, from a character named Ghostkeeper. But once the manuscript wound up in the hands of a small press that wasn’t going to be worried about recognition value in Downers Grove, Illinois, or among the knuckleheads at a sales conference, I went back to Wittgenstein. “Mistress” had been on the same scratch sheet with “Niece,” and I decided I liked it better by then.
JT: And meaning basically that your heroine is mistress to Wittgenstein’s thought?
DM: Well, along with several other people’s yes. But as I started to say a few minutes ago, the Wittgenstein is frequently most obvious in the very way she questions so many of her own “propositions,” as it were.