It's from a shorty story by, I think, Harlan Ellison. I can't remember the name of the story anymore, but it was magical realism and situated somewhere in England. The main character was a member of this gentlemen club, but used most of his time hunting phantasms, or fey. Musopticon, along with oneiroscope, was a machine, resembling an unholy union between a gramophone and an old-style telephone, to detect them.
As for why I chose it; it was Victorian like hell. And I was really desparate for a name that was both obscure enough to be unique, yet still be (almost)non-fantasy. Otherwise I would have started with some other recurring nick(I've used this, or variations of it, like Mousepants, on a dozen fora), which probably might have contained an apostrophe. The name is not terribly clever, but at least it's not Kil'Jaeden. The question mark comes from the wtf-factor that's always present.