I am familiar with the hypothesis that you assert, but don't find it compelling, or useful.
Oh, I imagine you don't. It is, nonetheless, accurate.
Note too the taxonomic rule, that the earliest name given to something is the one we are to use. All words, in a sense, are the name given to some object, concept, thing, according to the original definition.
Has that
ever been followed? I doubt it. Go to the cities of Italy and observe how the local name is much, much different than the name you're familiar with. I.e. Florence/Firenze.
The very existence of more than one language proves you wrong, and proves that "hypothesis" to be fact.
There are symbols, and there are referents. But referents themselves can only be decribed in words. All words reduce only to words. There's just no way to define a word except as other words.