Welcome, boncos; but oh dear oh dear I am having a terrible time, trying not to put an r in your name! I had to look up nosism:
A.Word.A.Day--nosism

This week's theme: There is a word for it.

nosism (NO-siz-em) noun

The use of 'we' in referring to oneself.

[From Latin nos (we).]

As it's often used by editors, it's also known as the "editorial we". It's also called "the royal we" owing to its frequent use by royalty. Mark Twain once said, "Only kings, presidents, editors, and people with tapeworms have the right to use the editorial 'we'."

-Anu Garg (words at wordsmith.org)

It made me smile because it sounds like it refers to people who stereotypically have their nose in the air!

Can't help you on the origin, I fear; but I've only read it in British novels. You might try going to I&A (Information and Announcements) and open either of the Useful language links threads. There's an amazing list of resources there (thanks yet again, MaxQ).