A persona in the word's everyday usage,
is a social role or a character played by an actor. 

The word is derived from Latin, where it originally referred to a theatrical mask. The Latin word probably derived from the Etruscan word "phersu", with the same meaning, and that from the Greek πρόσωπον (prosōpon).

Its meaning in the latter Roman period changed to indicate a "character" of a theatrical performance or court of law. 
Powers, and duties followed the role.