@freemo Roots of the language and of the writing system are not necessarily the same. There were multiple instances of significant import of "characters" from ~Chinese into Japanese and I had the impression that at least some of them didn't import much past the characters themselves.
My vague recollection is that there was oneish root of ideograms, but the languages evolved before writing in an unrelated way. I don't know how much adoption of writing affected the languages.