ark from Old English:
Aerc was the Old English word for a chest, from Latin arca ‘a chest or box’. This developed into ark, as in the Ark of the Covenant, the wooden chest in which the tablets of the laws of the ancient Israelites were kept, and the Holy Ark in a synagogue, a chest, or cupboard which contained the scrolls of the Torah or Hebrew scriptures. A ship may be thought of as a floating container, hence Noah's Ark, the vessel built by Noah to escape the Flood. The Latin word is also the source of arcane (mid 16th century), which describes something hidden, concealed, or secret, as if it were shut up in a box, which only a few people can open.
arca←拉丁语arca（箱子、盒子）←原始印欧词根ark（容纳、包含）
arcane = arca（箱子、盒子）+ ne（形容词后缀）→藏在箱子里的→神秘的
在具体使用时， arcane 并非用于形容那些超自然或魔法巫术之类无人能懂的东西，而是 强调造成常人无法理解的原因在于秘密只有其拥有者等少数人知道 ，比如：
晦涩的行话 arcane jargon
对不谙金融界事物的人而言如同天书 seem arcane to those not closely involved in the world of finance