Vulcan, the great smith and metal founder of the gods. He was the son of Hera - according to Hesiod, without a mate - and with Aphrodite as his wife became the father of Eros. As in so many cases, this is probably not a Greek name, although the root of his name certainly suggests 'to shine' (phao). Robert Graves thinks this, and proposes a derivation from a word hemerophaestos, 'he who shines by day', in other words - the sun! (For the first part of this word, see Hemera.)
However, this may be over-ambitious, and we would do better to consider some sense of 'shining' or 'light' with the first two letters of his name unexplained. (Possibly they were simply added for euphony, which means his name is exactly the same as that of Phaestus) Hephaestus, like Vulcan, seems to have been some kind of volcanic god originally, so that the 'light' would have been a burning, fiery one.