Sokkmimir

Sokkmimir (Old Norse: Søkkmímir; Icelandic: Sökkmímir) was a Jǫtunn who appears in two sources from Norse mythology, suggesting that he was once a well-known jötunn in Scandinavia.

In Grímnismál, stanza 50, it appears that Óðinn killed the jötunn:

He notably appears in Ynglingatal, where subterranean abodes of giants are called Sökkmímir's halls: