means A person who entertains an audience by acting, singing, dancing, playing music, or otherwise putting on a show.

from From the verb 'perform,' which entered English in the 14th century from Anglo-Norman 'parformer,' an alteration of Old French 'parfournir' — 'par-' (thoroughly, completely) plus 'fournir' (to furnish, provide, accomplish). So at root a performer is one who 'carries something all the way through' — the meaning narrowed over time from completing any task to executing one in front of a crowd. The '-er' is the plain English agent suffix, the same that turns 'bake' into 'baker.'