Wikipedia
Zemlyanka ( Russian or , ) is an Eastern Slavic name for a dugout or earth-house which was used to provide shelter for humans or domestic animals. Based on a hole or depression dug into the ground, these structures are one of the most ancient types of housing known. Zemlyankas can be partially or fully recessed into the earth, with a flat roof covered with branches or sod, or dug into a hillside. The use of natural earth for insulation and protection for underground living has evolved into the " earth shelter" technology used today in architecture.
Zemlyanka was the name for a German-Soviet War song written by Alexey Surkov (verses) and Konstantin Listov (music) in 1941 during the Battle of Moscow. The use of zemlyankas by soldiers is mentioned in the song.