"Are you asking if there's any reason, beyond accidental, for the association of specific codes with particular amino acids? There are some speculative ideas floating around about this, but little experimental evidence."
Yes, that is precisely what I'm asking - do you happen to know what any of these speculations involve?
This Wikipedia article has a couple of speculations, with links, at the very end. One is that certain amino acids actually bind selectively to certain codons, even without tRNA. I'm interested, if rather skeptical. More likely is the second paper, whcih suggest that the number of amino acids was once significantly smaller, and that the codon - amino acid links branched. I find this much more plausible, since it gives one an evolutionary pathway from a simpler genome.