Admit it. You say that phrase don’t you.You split the word “another” into two words. The word “nother” does not exist. As a matter of fact, there is a red squiggly line under it as I type. Why do we put this word asunder? Does it sound awkward to you when you say it? Really, what you’re saying is “another whole” something. But our minds are subconsciously wanting to say “a whole other.” But, as we all remember from elementary school, if you use “a” before a word that starts with a vowel, you have to use “an.” This rule engrained into us a children forces us to use improper grammar and divide the poor word “another” in two!
I don’t have an answer to why it happens, but we either know someone who says it (and frequently) or we use it ourselves to the shame of Mrs. Kimbell. It’s likely because we think the word is A-nother, rather than an-OTHER.
A whole nother thing that bothers me (see?) is when someone says they “could care less.” …………. If you “could care less,” then why don’t you do it? You wouldn’t tell someone “I could love you more.” If you want to tell her your love is at its maximum output, you would say, “I couldn’t love you any more.” (Note the space between “any” and “more.” Otherwise, that sounds awful and is the exact opposite of what you mean to say. Otherwise, just say something else.)
The point is, you shouldn’t fall short when using common phrases. Good grammar will help with stuff that you wanna say. After all, if you say what you mean, you’ll never have to correct yourself. But that’s a whole nother subject.