"Nea" is sort of "Aden" with the sounds in the wrong order. Ay-[d]N = [d]N-ay, with the "d" sound being that not-quite pronounced, "dead" consonant.This sound is quite common in English but hard for them to get around in words. Or, possibly he's hearing the D sound but just missing it off, as missing the first consonant sounds off words is really common as well.
DS does this a lot on new, complicated or unfamiliar words. E.g. Barstick for basket, for ages he would call our cat, Bernard, Birnden. A hilarious one was brown-eye for eyebrow
And for ages he said my, instead of I'm (which is a perfect example of the sound-inversion as in your Aden example) and still quite often says my instead of I. "C" is often "T" or "D" - I have a family member called Catherine who was "Damin" for ages, then "Tamin," "Tafin" and now "Tafrin" It's just an easier sound for them to make, even if they make it correctly in other places in words - DS' first word was "Look" for example which has the C sound at the end and yet he's only recently started saying car instead of tar.
He's just 3 now and though I can understand him perfectly 99% of the time, others still sometimes look puzzled and look to me to ascertain what he is saying. I don't think he tends to use his own name much, recently he's found it very funny to pretend to be me and then insist "You are !"
Definitely agree to avoid any kind of questioning or teaching process. Just keep on using the correct word around him and he will pick it up. Don't correct him or keep testing him or asking him to say things etc. (I don't even go out of my way to repeat words back to him correctly. It just seems to make a bigger deal out of it than it should.) Your DS sounds like he's doing great :) And it's quite cute/funny to see what interesting alternatives and in-between words they come up with! My absolute favourite was wuddles, for puddles. And at the moment he's particularly concerned by people having forms stuck to their feet, or in their clothes, or in their eye (he means thorns - in other words any small, sharp or annoying thing
)
Names seem particularly hard for them to grasp, by the way. I don't know why that is. But I know of so many families who have a relative or a grandparent with a strange, nonsense-sounding nickname, which came from a small child learning to speak, and they were so delighted with it that it stuck.