Publisher "s.n."

When a hymnal's publisher is given as "s.n.", does this mean "sine nomine" (not the tune; the phrase) or what? And (this is why I'm asking here instead of in the User Room) is this standard Hymnary jargon, i.e. should I use it instead of, say, "None" or "Unknown", if I'm entering a hymnal to which it applies? Or is it a leftover from a bygone era, a DiNAH-sore, as it were, to be replaced (with what? when possible? I just ran into it in Watts, here, on a quest for the first publication of "With sons and honours sounding loud". Don't recall running into it here before.