It means "holi" in Sanskrit. Sorry, I couldn't help myself. I've never seen an etymology for it. Here's what Monier-Williams has to say in his big ole Sanskrit dictionary: holaka. f. (perhaps from a cry or shout or sound in singing), the spring festival at the approach of the vernal equinox (commonly called Huli or Holi, and said to be dedicated to Krishna and the Gopis; it is celebrated during the 10 days preceding the full moon of the month of Phalguna, when people sprinkle red powder in sport and light fires; in some parts of India the Holi festival corresponds to or immediately precedes the dolayatra, q.v.)" I'm sure maahey or shanks can give the modern spin on it. Phalguna means 'reddish' and dolayatra means 'swing (ing of images of Krishna as a boy) festival, 14 Phalguna'. Our tilt is related to dolayate 'to swing' whence dolayatra above. It's always sounded like fun, but I've never experienced one firsthand.