Has Japanese always had the "polite form"?
Japanese has what is known as the "polite form" and the "plain form". Notably, the two forms have completely different conjugations despite having the same meaning, differing only in politeness. My question is, has this grammatical politeness always existed? And if not, when and how did this construct arise?
Intuitively, I would think that it would have had to be added on at some point, since the Japanese language and its grammar probably predates social constructs such as levels of politeness. I can't seem to find any research on this topic though.