Named after Valdemar Axel Firsoff - English astronomer (1910-1981).
Parts of the crater display many layers, as do some of the other craters in the region. Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mars large craters are named after deceased scientists, writers and others who have contributed to the lore of Mars. Small creaters (less than 60km) are named after small towns and villages.