I read a former question regarding the usage of "whole nother." I have a theory on this phenomenon.
I believe that the construction of "another" almost sounds like article ("a") plus noun ("nother") Even though we consciously KNOW that these are not two separate words, perhaps our tongues forget this fact. (I thought of this when listening to a Pink Floyd lyric: All in all we're just a (beat) nother brick in the wall." The break between the two letters would make a non English speaker probably assume it was two separate words and English speakers may've formed this habit due to the construction of the word...okay there's my two cents!!!!