Namine is Latin for "named", which is actually spelled NOMINE, but its still pronounced the same way

[yay me for taking Latin X) oO but then NOT yay kuz the class totally SUCKS.. so my advice to you is DO NOT TAKE LATIN IN HIGHSCHOOL; ITS FUKN BORING AS HELL! even if you think its going to be easier because its cloce to english, its not; the words actually annoy me X< t-t im so happy that this year is my last year in that class ]

Namine isnt JUST a nobody; shes the only one who can control memorys and who doesnt [exactly] have a wepon, so she doesnt deserve a Nobodys name [i sapose] because she could even mess with someones memorys to make them think theyr someone else; thus SHE is the one NAMING them

and the reason why Namine doesnt have a Organization jacket is kuz they let her wair the cloths she came to them in; same reason for Twilight Town Roxas's clothing

Even though my reason doesnt exactly explain WHY they didnt give her an X, it does explain the reasoning behind the name, so i hope this tip helps out with KH's inconsistencies