And the same in Commedia dell Arte, Italian for ‘Play of Professional Artists'. They were travelling troupes performing at streets or market squares where it would attract viewers. It was a popular form of theater developed in Italy. Its popularity lasted from the 1500s through to the mid 1700s during which time, it spread through out Europe. They usually did physical comedies involving exaggerated and boisterous actions, a precursor to Charlie Chaplin, and a theatrical form still being taught in today's drama schools with performance being moved from streets to theater halls. All stock characters wear masks except the lovers - guess romantic love is the only area that no mask is allowed!
In our common everyday language, we don't like being labeled as wearing a mask. We like to be considered as truthful, honest, baring our soul, instead of wearing the mask of a peddling salesman, even when we intend to convince others to take our views. To make our life easier (off-stage), we do expect people to wear mask in their different roles. Given the possible negative connotation of hiding behind a mask, we credit such behavior as being professional. A waiter or waitress is expected to wear a happy mask, whereas a customs officer at borders is expected to wear an intimidating mask. Both acted professionally.
Sometimes a mask will fail on stage as well as off stage, the former we call "poor performance". Many years ago, a friend told me that he had this lousy secretary who filed his letters incorrectly and faxed his correspondence to the wrong number! He finally couldn't bear it any longer, and asked her into his office to confront her in person. Having educated in the best Univeristy, he acted in the most professional way of being a benevolent manager and wouldn't want to hurt the feeling of his secretary. He talked to her in a smiling face, and always explained her shortcomings with the classic "yes, but". Get the affirmative first before delivering the negative. After one hour of counseling, the boss became very nervous. He began to sense that his secretary was expecting he gonna tell her that he would give her a raise! In all desperations, he changed his mask and turned into a solemn face: "You're fired!"