Paschen is a lunar crater on the far side. The large satellite crater Paschen M partly overlies the southern rim , and they nearly form a merged pair with only a section of irregular terrain along their common border. The smaller but well-formed crater Paschen S lies across the southwestern rim. As a result, most of the southern rim is now gone. (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.