"Arcane knowledge" refers to information or understanding that is obscure, secret, or known only by a few people. It often involves mystical or esoteric teachings that are not easily accessible to the general public. Full definition
It's not a magical book that requires arcane knowledge to decipher and understand. (redeeminggod.com)
But you forgot the Kabbalah, which many gentiles think is cool It's like Jewish gnosticism Arcane knowledge. (redeeminggod.com)
It's the kind of intrigue that forms the basis of much of Barker's work: the hidden grotto, arcane knowledge secreted away, art too beautiful for human eyes. (filmfreakcentral.net)