The first OED citation is 1914, so presumably it was circulating before then, and it would only be natural for a SLytherin to keep up with German politics, what with the Durmstrang connection and so on. I had assumed it was earlier, but looked it up because I was curious as to how much earlier. I didn't actually intend to be over nitpicky, but I seem to have acheived it!

Re. leaning, I suspect option 2.