Was my teacher wrong in it not usually being written as Ud. particularly in signs and stuff?
The abbreviation is rare in general; mostly I see it used in a few fixed formulas and in places where space is limited (which may include signs), but as Ají pointed out, in general in Spanish we tend to abbreviate by ellision rather than to use abbreviations.
So, rather than “deposite usted el contenido de sus bolsillos en otra bandeja” (place the content of your pockets in another tray) or “*deposite Ud. …” *you’d just see “*deposite el contenido…” *or, shorter, “vacíe sus bolsillos en otra bandeja” (empty your pockets into another tray). All of them use the formal mode of address, but in the last two the subject is ellided.
Oh, and sometimes the abbreviation is written as Vd.
for Vuestra merced?
I’ve never been clear on why, I’ve heard some people say it’s for Vuesa merced (but they can never provide an example, and Vª M[sup]d[/sup] has its own abbreviation) and others guess that it hails from a confusion between V and U (which look very similar in many people’s handwriting). It’s a sort of Spanish OK in that you can find many WAGs but not anything that looks really solid.
Per the* Diccionario de la lengua española*, usted comes from vusted, and looking up vusted it mentions that it comes from vuestra merced.
There’s also a third, “vos” which is used in Bolivia, Nicaragua, and maybe some other places. This basically takes the place of tu in those places, making tu formal, and usted really freaking formal.
Sounds like a Droogie insult. Source?
Probably most typical of Argentina/Uruguay/Paraguay, and used in other Central American countries as well as Nicaragua.
Anthony Burgess, IIRC. An author who used to converse in ancient Anglo-Saxon with Jorge Luis Borges at Argentinian embassy parties to evade the ears of Argentinian secret police. How cool is that? No doubt they called each other þū.