harry potter - Why did Tom Riddle change his name to Voldemort?

Why did Tom Riddle change his name to Voldemort? What was the point of Lord Voldemort, specifically, not Lord Tom or, Lord Riddle? Tom Riddle was his officially documented name, after all...

Answer

Voldemort despised his Muggle father, who was also named Tom Riddle for 1) being a Muggle, something Tom Riddle Sr. couldn't help, and 2) for leaving his mother Merope Gaunt while she was still pregnant with Tom Riddle. I interpret canon to mean Tom Riddle took on the moniker "Voldemort" mainly to distance himself from the name Tom Riddle and his Muggle side of the family. He also wanted a name that wizards and witches the world around would fear to hear or speak. "I am Lord Voldemort" from Chamber of Secrets is an anagram for Tom Marvolo Riddle.

‘You think I was going to use my filthy Muggle father’s name for ever? I, in whose veins runs the blood of Salazar Slytherin himself, through my mother’s side? I, keep the name of a foul, common Muggle, who abandoned me even before I was born, just because he found out his wife was a witch? No, Harry. I fashioned myself a new name, a name I knew wizards everywhere would one day fear to speak, when I had become the greatest sorcerer in the world!’

_{Chamber of Secrets - page 231 - UK Hardcover - chapter 17, The Heir of Slytherin}

I researched it and apparently "Voldemort" means "flight of death" in French (Vol de mort). I confirmed this with Gilles, who is French, and he said it can also mean "theft of death." Either are appropriate when one reviews Voldemort's primary objective to avoid death, to essentially steal his own death away from the inevitability of mortality by creating Horcruxes. This is just my personal observation -- J.K. Rowling's university degree is in French, and she taught French for at least two years. I'm not sure how she didn't know that Voldemort means flight of death. I'm certainly not suggesting she's lying; it's just interesting.