Named after Plutarch - Greek biographer (c. A.D.46-c. 120).
Plutarch is a lunar impact crater that lies near the north-northeastern limb , just to the south of the irregular crater Seneca. To the southeast is the flooded crater Cannon. The proximity of this crater to the limb causes it to appear foreshortened when viewed from the Earth, but it is actually a circular formation. This crater has a well-defined rim edge that is only slightly eroded. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.