Named after James Smithson - British chemist, mineralogist (1765-1829).
Smithson is a small lunar impact crater located in the northeast part of Mare Fecunditatis. It was previously identified as Taruntius N before being renamed by the IAU. Taruntius itself lies to the west-northwest, in the northwestern part of the same mare. (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.