A whole other just sounds dumb. To me adding the "n" is like adding the "n" to "a" before a vowel like an iceberg. Nother just rolls off the tongue better following a whole. I think it's a good thing

Perhaps it doesn't just come from one place. Maybe Greeks did mark things as O.K. Or OK and maybe people also took the word okeh and spelled it "okay" and so on, and they all just happened to mean nearly the same thing so we think it comes from a single origin