Herra Tohtori...
That is a character from a Finnish comedy sketch series called Kummeli, which is not unlike Monty Python, though the humour is quite different. Anyway, Once upon a time, I was at school and I posted a message at a certain forum (
www.tiede.fi/keskustelut, a Finnish science magazine's forum), then I had to come up with a user name real fast, and this just occurred to me. Chances are, if you see someone using the name "Herra Tohtori" in the net, that's most likely me. Haven't seen anyone else using it.
And if you see Trifid Nebula in conjunction with my nick, that's definitely me.

I use it as my avatar in quite a few places. This is how it looks like...

This is also one of the names that just stuck. It would be awkward to use other user name.
...What does it mean, then? It's Mr. Doctor in English... or Herr Doktor auf deutch. No, I'm not a real doctor. Neither medical or anything else.
Yet.