1) The Kamakura period (1185-1333).
2) A type of igloo made of snow, common in the 'snow country' parts of northern Japan. Kamakura are built in mid-February and occupied by children who cook and eat o-mochi and drink amazake, a sweet drink made from fermented rice. Offerings of sake (o-mi-ki) are made at a small altar in the igloo dedicated to suijin-sama the kami of water.
A Popular Dictionary of Shinto. Brian Bocking.