Mjölnir is the hammer of Thor, the god of thunder, in Norse mythology. Mjölnir was considered as one of the most powerful weapons in existence and was capable of leveling mountains.
The name Mjölnir originates from the root of the Germanic word malanan, which meant "to grind". From that it came to mean "the grinder".
The correct pronunciation of Mjölnir is Mee-ol-neer. The most difficult part to pronounce is the final "R", which is pronounced as a rolling "R", as heard in the audio pronunciation. The "ö" in Mjölnir is pronounced in a closed way that can be unfamiliar to English speakers, but is similar to the "ough" part of the word "thought".