I could suggest asking him about the double l's. IME, gifted kids usually do things that don't make sense to us but make sense to them...i.e. they spot a pattern that others don't see

Or maybe he just likes it that way.

I have a friend whose name is Lloyd. Never occurred to me to find out why there are two L's at the beginning of his name...

Beyond that, a language arts specialist can tell you why and also tell you what to do about it. Can you find someone nearby? Probably need a couple hours of evaluation and ask them to write up the recommendations for the next step.

That being said, he is certainly developing much more rapidly than the average kid his age and I think you are right to question whether or not to go to kindergarten.

"Normal can never be amazing." - Mini USA