In some languages, and localized areas of the English-speaking world, plaster is mineral specific, such as a gypsum-derived material, or “use specific,” such as a coating applied on interiors. However, our English word plaster ultimately derives from the Greek emplastron (εµπλαστρον) meaning to daub on.
So the term plaster can rightly describe a variety of interior or exterior coatings that are daubed, thrown or trowel applied.