Direct quote from the wikipedia article of [Mjölnir][1]
> hammer of [Thor][2], a major Norse god associated with thunder. [Mjölnir][1] is depicted in Norse mythology as one of the most fearsome weapons, capable of leveling mountains. In his account of Norse mythology, Snorri Sturluson relates how the hammer was made by the dwarven brothers [Sindri][3] and [Brokkr][4], and how its characteristically short handle was due to a mishap during its manufacture.

[1]:http://nl.wikipedia.org/wiki/Mj%C3%B6lnir
[2]:http://en.wikipedia.org/wiki/Thor
[3]:http://en.wikipedia.org/wiki/Eitri
[4]:http://en.wikipedia.org/wiki/Brokkr