sirgregory wrote: Thinking about the Spanish pronouns for a minute, the tú and vosotros are of course similar to the tu and vous in French. Spanish adds "others" to the vos. This seems unnecessary but I guess it makes sense ("you others"). I'm pretty sure this was because at one point vos also functioned as the polite singular (before being supplanted by usted), so presumably they added the otros to distinguish the singular and plural vos forms. It's actually very similar to what's going on with "you all."
It even got to the point where
vos was not only used as the polite form, but also started to be used as the familiar form in the singular. This gave rise to the
voseo phenomenon in Latin American Spanish.
sirgregory wrote:One curiosity though is why they added the otros to nos. Again, in French they get by just fine with nous. And there would be no ambiguity if nos were used by itself in Spanish. So why was it added? Was it just to have that catchy nosotros/vosotros rhyme?
Yes, most likely by analogy, between
nos and
vos,
nosotros and
vosotros. There was some room for ambiguity with
nos too though, the "royal we":
Nos, rey de España.
For those who don't know it,
usted is historically a contraction of
vuestra merced. That's why it grammatically functions as a third person pronoun.