Frantisek; Czechoslovakian astronomer (1867-1925). (Spelling changed from Nüsl.)
Nušl /ˈnʊʃəl/ is an impact crater on the far side. Diameter of the crater is 61 km. Its mean depth is about 3.8 km, but the full range of heights reaches 5.2 km. (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.