In Norse mythology and Asatru (according to the Eddas), Fimbulwinter is the immediate prelude to the end of the world, Ragnarok. Fimbulwinter is three successive winters without any intervening summer.
During this time, there will be innumerable wars and brothers will kill brothers.
The original spelling of this word in the Old Norse language is Fimbulvetr, fimbul meaning "the great/big" so the correct interpretation of the word is "the big winter".
There have been several popular speculations about whether this particular piece of mythology has a connection to the climate change that occurred in the Nordic countries at the end of the Iron Age. Before this climate change, the Nordic countries were considerably warmer.
In Sweden, Norway and other Nordic countries, the term fimbulwinter may also casually be used to refer to any unusually cold and harsh winter with lots of snow.
