[The Squatter of Amon Rûdh]

I think that sometimes it detracts from the subtlety of Tolkien's use of the old myths to make direct x=y comparisons between them. Clearly there is a correlation between Fenris and Carcharoth, but I don't think it's one of equivalence. For example, Tyr is only required to put his hand into the wolf's mouth to prove the non-existent good faith of the Æsir. Without that guarantee the wolf will never allow himself to be bound with the great chain Gelgja, which is clearly parallelled by Angainor elsewhere in the Silmarillion. The loss of Beren's hand, by virtue of the Silmaril it holds, doesn't so much bind the wolf as loose it on a destructive rampage. Fenris is, according to Gylfaginning, fated to die at Ragnarok, when his jaws will be wrenched apart by Víðarr. Interestingly, the same source records that Tyr is destined to be killed by the great dog Garmr, and not by Fenris, who will have his jaws full swallowing Oðinn. In other words, Fenrisúlfr is killed in a battle by a character other than he whose hand he took; Carcharoth is killed by Beren during a hunt, although there is a possibility that this is taken from the fight between Tyr and Garmr. The use of the lost hand motif in the story of Maedhros seems to me to suggest that it had a particular hold on Tolkien's imagination, regardless of the particular myth in which he found it. A particularly amusing parallel, which Tolkien may have included on purpose because of the irony, is that the Silmarils contain the light that was before the sun, whereas Fenris is destined to swallow the sun itself. It could well be that he wondered how an animal might feel were it to consume a star, and developed his myth accordingly.

The significance of the whole story has, of course, changed entirely. Carcharoth lacks Fenris' important and apocalyptic role in the Norse myths, being rather one of a series of characters encountered by Beren and Lúthien in their own central and significant quest. For me this is typical of Tolkien's mythologising technique. We can trace this compression and recontextualising in the tragedy of Túrin and Glaurung, which borrows elements from at least two separate legends. The story of Turambar and Glaurung was inspired at least in part by Sigurð's slaying of Fafnir in Volsunga Saga and that of Túrin and Nienor echoes a theme from the story of Kullervo in the Kalevala, but his story takes elements of these and applies them to a new narrative context, using them as building blocks for new legends and tales. One could develop literature as diverse as Beowulf and Hrolfs Saga Kraka from these plot elements (as, in fact, two medieval writers did from the legends of the Scyldings/Skjoldungs), but Tolkien goes further in that he builds them into entirely new stories, related to the originals only by a complicated reverse engineering that suggested to him legends that might have developed into those which history has recorded. Such is the case with Ælfwine, who in HoME V extemporises a poem very closely related to the text of the Anglo-Saxon elegy The Seafarer, but which provides a potential 'pure' form of that somewhat corrupt poem. Since this theme was never fully expressed or realised, it's difficult to see how far Tolkien would have taken it in a published Silmarillion, or even whether he would have made it explicit at all. It may even have been a passing phase, eventually forgotten as the philosophy of his own myths became his primary preoccupation.

Essentially, then, Tolkien's use of Germanic mythology is more one of inspiration. A name, an event, a plot device would grasp his attention and then be worked into his insatiably acquisitive legendarium. Doubtless Fenrisúlfr has been included, as have the Old English word Earendel, Sigurð/Siegfried, the mysterious Sheaf and Alexander's Letter to Aristotle (in which is contained a description of the trees of sun and moon, the parallels of which need no elaboration). How far Tolkien intended to make his characters the imaginary prototypes for known mythological beings is still not completely clear to me. In places the process seems almost unconscious, in others it is developed to such a sophisticated degree that it must have been carefully thought out. Even so, I don't think that we can call the Carcharoth of the Silmarillion 'Tolkien's Fenris' solely on narrative grounds, since he plays a far less apocalyptic role, not to mention not actually being the son of Morgoth. Rather he is a character inspired by and similar to Fenris, yet with a significantly different part to play. Of course the similarities and direct borrowings are many and varied, but Tolkien reached a highly developed version of Beren's story very early in the history of his mythology, before he really achieved his full stature as a writer; I suspect that he would have handled the real-world mythological elements with more subtlety in his later years, and I would have liked to see a Silmarillion complete with Ælfwine as a real-world arbiter.