The word means ‘face’ in old Dutch. In seventeenth century low countries, Baroque Flemish artists began to favour a certain genre we now term tronie. The artist would for various reasons, not excluding practice, paint exaggerated facial expressions such as a surprised face. Unless it was practice as is the case with some of Rembrandt’s self portraits, the sitter remains unidentified to this day. The sitter is then the equivalent to an extra in the cast of a movie. Even if the identity of the person was not important the works could still be intended to be a serious piece of work.
Three Vermeer paintings are now considered important “tronies”, with the more famous of them being the Girl with a Pearl Earring
In the cases, where the sitter is identifiable, he or she tended to be someone dressed up in some classical historic costume enacting something religious or mythological from the past. It was everything from a prank to portrait historié.
The important part to take away from all this is that who owns the face is less important that what the face expresses in the right context.