[jallanite]

Originally Posted by Zigûr

I am of course assuming the Dwarves knew of Bombadil before they adopted Northern Mannish as their public naming language, however.

Possibly the Dwarves knew of Bombadil before adopting Northern Mannish and possibly they didn’t. The name Forn is presumably a current name for Bombadil originating among Dwarves who took names of translated Norse.

Similarly, of course, the name 'Durin' was given to the Dwarven ancestor retroactively in the tongue of Northern Men long after Durin the Deathless' own time …

In The Peoples of Middle-earth (HoME 12), page 304, J. R. R. Tolkien attributes the name Durin to the Men of the North of the Second Age, and states the name was a word for ‘king’ in that language. But Durin in Old Norse is not related to a word for ‘king’ so far as I know. It may be from dyrr ‘door’ and be intended to mean ‘Door Warden’ or from the stem dúrr- ‘slumber, sleep’ and mean ‘Sleeper, Sleepy’.

In a note on this statement Christopher Tolkien notes that his father here seems to accept Durin as the ‘real’ Mannish name of the Father of the Longbeards, but that name is a name derived from Old Norse, so it must be a translation. But I’m not sure that J. R. R. Tolkien did not, in this case, understand it as a genuine name meaning ‘king’ that by coincidence was the same as the genuine Old Norse Dwarf name Durin.