A nosism is the term for using 'we' to refer to oneself. I am looking for a term for/etymology of using 'we' to mean 'you'.
EDIT: Another way of putting it is that I'm looking for the proper term for "the patronising we" (made up) that is mentioned here.
In the UK, it is somewhat commonplace to hear people (usually of higher authority than the other person) to use 'we' and/or 'our' in place of 'you' and 'your'.
I had a teacher who always used to do this and have ever since wondered why. For example:
Teacher to student: Why aren't we doing our homework?
(Why aren't you doing any of your homework)
We need to start getting that planner signed.
(You need to start signing your student planner)
It's sometimes said with a rhetorical question at the end ("__, are we?")
6. pron. Used confidentially or humorously to mean the person or persons addressed, with whose interests the speaker thus identifies himself or herself (esp. by a doctor in friendly or cheering address to a patient); also used mockingly or reproachfully by a parent, intimate friend, etc.
I've also realised we is often used in the second-person plural for 'you (all)'. For example, a waiter might ask a group of diners:
How are we doing over here?
What's the origin of this, what's the proper term for it and please tell me this isn't exclusive to a few people's idiolects.