Hassium was first made in 1984. and eka-osmium. It was made at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany. The element was named from the Latin name for the German state of Hessen. Hessen is the state that the Gesellschaft für Schwerionenforschung is in. Before it was named Hassium, scientists could not decide what the name should be and there was an element naming controversy. The temporary IUPAC systematic element name was unniloctium meaning "one-zero-eight-ium" referring to its atomic number. The symbol with the name was Uno. In 1994 a committee of IUPAC recommended that element 108 be named hahnium. The name hassium was adopted internationally in 1997.
Isotope 270 of Hassium was found in December 2006. An international team of scientists led by the Technical University of Munich discovered it. It is a doubly magic isotope and it has a long half-life of 22 seconds. Scientists had thought that heavy and stable isotopes should exist. Some theories said Hassium-270 may be part of an island of stability. Hassium can oxidise like osmium, the element above it in the periodic table, into hassium tetroxide. Chemists found that is less volatile than osmium tetroxide.