Named after Ionnas (Jean-Henri) Focas - Greek/French astronomer (1909-1969).
Focas Crater is an impact crater in the Ismenius Lacus quadrangle of Mars. Focas Crater is 76.5 km in diameter. (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.