I used to say as much to a research partner when I'd clock out for the night and he was still hunched over his work top. [He might actually sound wryly amused, though inwardly, there might be the tiniest pang of regret.]

[Unwittingly mirroring her a bit, he clasps his hands behind the small of his back, at-ease style.]

I suppose the simplest explanation is that one is my work name, the other is my own, or at least the one which I used for so long that it has become as a true name. There's also still some Sleepers who remember me by that name, thus their memory keeps it cogent.