What do you mean by an old soul ? Many Japanese think that we have 魂. But I ve never heard of 古い魂.

「古い魂」is sytactically possible. I don't know what it means by "old soul" . What is this? I would say, giving 古い魂 lots of decorations without knowing its meaning, 「古（いにしえ）の心」「古（いにしえ）の魂」「古き御魂（みたま）」. These are old-fashioned buzz words. (I don't like them). >if I wan to describe a young man with wisdom as having 古い魂をもった若者. Then it could be「古（いにしえ）の叡知そなえし若人（わこうど）」, also a buzz expression which is often used in Japanese role-plaing games.

はい！「古い魂｜は正解です。でも、ほかの同じ意味がある言葉が分かりません。

In Japanese OLD 古い has a rather negative connotation. Old clothes, old books, old man/woman etc. In Japanese, for living humans we use: 人格、品格、and for Spirits:じょうぼん上品、ちゅうぼん中品、しょうぼん小品の魂　／　霊格の高い、低い魂　／　熟度の高い、低い魂、成熟した魂、未熟な魂、　などの表現があります。 ＊Old Soul の単語が知りたいです。＊じしょ＝辞書では見つかりませんでした。＊他の言葉はありますか？