The ability to associate objects with phonetical sounds...

[Peter_20]

Agreed about hindsight. There most likely isn't some odd, mystical force behind words, syllables, or letters that fecundates them with inherent meaning. More likely, you just associate certain words or phonemes with what you've been told they mean over many years.

I don't think that's the only reason.
Sure, you do associate words with their meanings, but you can actually tell what it is from the phonetic ring of the word.

For example, words like "nim" and "mor" (Tolkien power! ) - it's obvious which words mean "black" and "white", because of the "bright" and "dark" sound.

I'm not talking about "recognizing" words, but rather about "feeling" them.

What would happen if the words "flower" and "death" switched meanings? Would people say that flower sounds scary, and that death sounds sweet-smelling and innocent?

You would indeed get used to the change with time, but you probably would think the words had little to do with the objects they stand for.