sound-symbolism isn't really something that develops along with a words etymology though
hmm... how to say this... maybe... Given all the sources for words in a language, sound symbolism is an advantage on the "natural selection" part of language evolution... but this can be quite distinct from a common root of a particular sound to a meaning.
Well, I'm just learning, but here is what I think based on what I've read:
There are two accent phrases わたしの（LHHH)｜はなです(LHHL) . The first one has no accent, the second one has an accent because of で↓す. So when you run them together like a single phrase, it becomes わたしのはなで↓す（LHHHHHHL）