I just noticed a distracting piece of nonsense from a book published by Oxford University Press and it just proves why a healthy dose of skepticism is important to sway us from the ignorance born from credentialism. The moment we see some impressive name like “Oxford”, it's human nature to accidentally believe, “Oh, Oxford University! Well, anyone from there is surely never misinformed.” Guess again. We're only human, no matter where we come from.
As I was doing my daily perusal of Google Books, I came across The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World with a table of reconstructed Indo-European deities, therein claiming that the theonym Mars may be derived from an Indo-European root *Māwort- (c.f. Sanskrit Marutas) and that the theonym Vulcan may stem from *Wĺ̥keh₂nos. Now, in matters of theory, one may appeal somewhat to the mysterious unknown since it can never be known with absolute certainty whether an etymology provided is a correct one. However, we can know with reasonable certainty whether something is incorrect by way of a little bit of old fashioned deduction.
What's silly about these claims is that it's been known for some time now that Mars was originally an agricultural god, not a war god, and was further an import from Etruscan mythology. The Etruscan name for this god of the fields was Maris with an extra -i- between the ar and ess, which makes it rather clear that the name must have been borrowed into Latin from Etruscan, not the other way around. The Sanskrit name Marutas on the other hand specifically refers to wind gods. So neither of these pseudocognates can seriously be connected to this ad hoc reconstruction **Māworts. For what it's worth, I've suggested that the purely Etruscan name Maris is built on a verb mar “to harvest” which would be more fitting afterall for the name of an agricultural deity. A little more theoretically plausible at least than what's in this book, dare I be too bold to say lest future comments from studious viewers like you prove me otherwise.
Now onward to the name Vulcan or in Latin, Vulcānus. This name is likewise borrowed from Etruscan Velchan and its Etruscan origin is further substantiated by the several Etruscan deities whose names and epithets end in -an. Names such as Turan, Sethlans and Alpan, for example. Personally I would suggest that Velchan can be broken down in the Etruscan language as velχ “hidden” (< vel “to hide”) and is then a direct Etruscan parallel to Greek Hades (said to be from αιδης aidēs “unseen” < PIE *n̥widḗs) which means the same. (Interestingly, the name of the Egyptian god of the setting sun, Amon, also means “hidden”. Coincidence?) Then the fact that the chthonic functions of both Hades and Velchan overlap also helps out my hypothesis nicely.
Later on page 410, we read: “[...] the amount of irregular sound change one has to assume, in the absence of an exact semantic equation, is more than most historical linguists are prepared to accept.” However, this is a naive assessment of these etymologies since historical linguists quite rightly should not be prepared to accept something that is ignorant of important historical facts.
Despite this controversy, other names reconstructed for Proto-Indo-European such as *H₂éusōs “Dawn” and *Dyēus-Ph₂tḗr “Sky Father” are much better attested and may be considered more genuine.
 Mallory/Adams, The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World (2006), p.409 (see link).
 Funk, Thereby Hangs a Tale - Stories of Curious Word Origins (2007), p.184 (see link).
 Padel, In and Out of the Mind (1994), p.99 (see link).
 Frankfort, Ancient Egyptian Religion (2000), p.22 (see link).