Not long ago, my Mythgard fellow, Luke Baugher, posted an intriguing essay here on Tulkas and Sir Gawain and the Green Knight, in which he argued that a connection may well exist between the word tulkes in Gawain and the Vala Tulkas in The Silmarillion. Though as Luke pointed out there was no way to prove that Tulkas' name originates in this way, the suggestion makes a great deal of sense.
Now one thing everybody loves about Tulkas is Tolkien's comment that he is 'of no avail as a counsellor' (Silm. 29), which does not fit particularly well with túlkr, the Old Norse word meaning 'interpreter' or 'spokesman' that is the source of tulkes. Yet, as Tolkien's comment above and his behavior elsewhere plainly show, he is by no means above a joke.
Nor, I would suggest, is he above two jokes here, the first being the obvious one at Tulkas' expense, the second, the more ironic, philological joke of deriving the name of Tulkas, ultimately, from a word that suggests he should be a useful counsellor when he is in fact precisely the opposite.
Ah, Tollers! A philologist's work is never done.