Garm: Hound Dog of Underworld or Another Name for Fenrir?

In Norse mythology, Garm was the name of the dog or wolf in the Underworld and was closely connected with the force of destruction. Little is known about this figure because of the contradictory details from materials. Yet, Garm is also a Norse figure worth our attention in this day and age. 

Grímnismál, one of the famous poems from Poetic Edda, Garm was believed to be the superior canine just like Odin the Allfather to the gods or Yggdrasil to the trees:

The best of trees
Must Yggdrasil be,
Skíðblaðnir best of boats;
Of all the gods
Is Óðinn the greatest,
And Sleipnir the best of steeds;
Bifröst of bridges, 
Bragi of skalds,
Hábrók of hawks, 
And Garm of hounds

In Völuspá, another famous Eddic poem, Garm was also mentioned, but not as a hound, a wolf instead. 

Now Garm howls wildly
Before Gnipa Cave.
Chains will snap
And the wolf shall run.

In the Grímnismál, Garm was called as the hound while the Voluspa called him "freki" meaning "wolf". The sight of a wolf breaking himself free from the chains surely reminds us of the day Fenrir broke himself free to trigger off Ragnarok Doom of the Gods. Fenrir was tied up by the gods to prevent him from devouring the cosmos. But what was written in the fate would come. The two images of two wolves under the fetter finally smashed the chain definitely make us link Fenrir and Garm as one figure. 

Fenrir was bound to the rock by a magical chain by the gods 

Another detail to support this interpretation was that Garm fought against Tyr in Ragnarok. In other words, Tyr and Garm were the sworn enemies who finally slew each other in Ragnarok. Because before binding Fenrir up, Tyr was the one who volunteered to put his hand in the mouth of Fenrir to have Fenrir tricked. 

However, we might meet some trouble when thinking that Garm and Fenrir as the same figure. Because in Norse mythology, the one who finally killed Fenrir was Vidar the son of Odin the Allfather. With this detail, Fenrir and Garm were not one. 

Hel, Garm/Fenrir, and Jormungandr the Midgard Serpent 

In Vegtamskviða, another Eddic poem, When Odin was travelling to Helheim the land of Underworld, he met a dog along his way. This cemented the point that Garm was the guarding hound of Hel at the gate of Helheim. 

Then Óðinn rose, 
the enchanter old,
And the saddle he laid
on Sleipnir's back;
Thence rode he down
to Helheim deep,
And the hound he met
that came from hell.
Bloody he was
on his breast before,
At the father of magic
he howled from afar;
Forward rode Óðinn,
the earth resounded
Till the house so high
of Hel he reached.