Here's my answer about phonesthesia: https://english.stackexchange.com/questions/532061/why-do-some-words-with-similar-meanings-sound-similar-as-well/532065#532065
I got a comment on my answer saying: Are you kidding me, gelidus has nothing to do with brightness? have you ever seen snow? I mean, of course it's rare in Italy, but if we say that words are arbitrary, that also means that the connections are arbitrary, and non-connection is not the null-hypotheses.