In 2009 Rowling actually apologised to French readers for naming an evil character Voldemort as the following source shows:

http://metro.co.uk/2009/02/04/rowling-sorry-for-voldemorts-name-416158/

The article starts out like this:

JK Rowling has apologised for giving Harry Potter’s arch-villain the French name Voldemort, claiming she meant no offence to our friends across the Channel. The name means “flight of death” in French.

There is some ambiguity in this though: while it does indeed mean 'flight of death' in French she points out that it is meant to be English. However for those who don't know she's actually part French. She elaborates in this article too (as well as the potential ambiguity):

"I want to thank my French readers for not resenting my choice of a French name for my evil character," she said in fluent French at a ceremony during which she received the award from President Nicolas Sarkozy. "I can assure you that no anti-French feeling was at the origin of this choice," she said. 'As a Francophile, I have always been proud of my French blood. But I needed a name that evokes both power and exoticism," she said of Voldemort, Harry Potter’s nemesis in the seven episodes of the bestselling series. "Voldemort himself is 100-percent English," she added. Rowling said she was in fact part-French as she had a French great-grandfather who fought in World War One and was honoured for that in 1924 with the Legion d’honneur, the same honour she received for her services to literature. "I like to think that he would be happy to know there is a second Legion d’honneur in the family and that the books written by his descendant have given some pleasure in his native country," she said.

So the answer is this: the etymology of the name is that in French it means 'flight of death'; however it's meant to be an English name in Harry Potter. Whether she says this after the fact because she doesn't want to cause offence who can say but she? Whatever the case 'flight of death' makes perfect sense for Voldemort, doesn't it? Think about it: he's terrified of death (Rowling stated his Boggart would be his own corpse) and sees it as a sign of weakness, he made Horcruxes and he said to Dumbledore (I might have the quote off a bit - this is from my memory):

'Nothing is worse than death, Dumbledore!'

At first he was contemptuous of his mother believing his father was the wizard since why else would his mother not save herself if she was magical?

English or French it means 'flight of death' and this is what Voldemort wholly embodies.