Art historians. Until the middle of the 17th century, it was extremely uncommon for an artist to give his work a formal title. Most pieces were commissioned portraits or religious iconography, and there was no need for explanation. The only name a painting had was the functional identification—usually something like “Profile of a Young Woman”—found in the extensive catalogs of private owners. However, as markets developed and a culture of criticism arose, people needed a shorthand way to refer to Renaissance pieces. The more frequently a particular work was discussed, the more likely that critics and historians would reach an informal agreement over what to call the piece.