Latin occulere (ob plus celare, to hide) gave occultus, hidden. Medicine still says occult blood, hidden in the stool; astronomy says occultation. The noun the occult, hidden arts, is a 16th-17th century usage. The celare root also built conceal and, by the Germanic twin, hell and hall, the covered places.
The cultural career: occult as the bookstore section of banned knowledge, censored sciences, and suppressed truths. Much of the shelf was never hidden by anyone, only outcompeted, which sells fewer candles.
The etymological jackpot: hell descends from the Germanic twin of celare, the covered, hidden place. Occult and hell are cousins, concealment above and below, and every occult revival is, at root, an argument about what belongs uncovered.
Does the occult hide from us, or do we cover it over and call the covering knowledge?