I am having understanding. I am hoping my retalling of such information is good. I am not being skilled in magic, I am just knowing what I was taught by the shamans before I left Brigid. We also use markings so the spirits can be protecting us. It is why I am having such markings too.
There is a wisdom to it—we just say those with certain elements have certain traits. Or perhaps having those qualities is what causes one to develop magic. We have perhaps less of an answer than you, as we don’t even have folklore to explain it to agree upon.