Garmr, like how it was told in mythology, is a chained blood-stained fearsome hound that guards the entrance to the underworld. Yet that wasn't the only reason how the Unique Rank C Ragnarok Beast Garmr got its codename.
Its unique skill, Blood-stained Hound, gives the Unique Rank C Ragnarok Beast the right to claim the codename Garmr.
Different from Rank A Ragnarok Beasts like Cerberus which has Dark, Flame, Lightning, and Ice Elements, or the Rank B Ragnarok Beast Icarus which has Flame Element, Rank C Ragnarok Beasts can't or, rather, don't have any Element to integrate into their attacks.
However, among the Rank C Ragnarok Beasts are rare ones that have a unique skill.