Same is true in Spanish, where "usted" ultimately derives from "vuestra merced".

For a completely different example, "on" in formal French means something like "one" in English: a pronoun for a general, unspecified person; as such, it takes singular conjugations. However, in colloquial speech, it means "we" and has almost completely replaced "nous" as a subject pronoun.

Thus: "il est" (he is); "on est" (we are, colloquial language); "nous sommes" (we are, standard language)