occultyoudaoicibaDictYouDict[occult 词源字典]
occult: [16] Something that is occult is etymologically ‘hidden’. The word comes from the past participle of Latin occulere ‘hide’, a compound verb formed from the prefix ob- and an unrecorded *celere, a relative of cēlāre ‘hide’ (which forms the second syllable of English conceal). When English acquired it, it still meant broadly ‘secret, hidden’ (‘Metals are nothing else but the earth’s hid and occult plants’, John Maplet, Green Forest 1567), a sense preserved in the derived astronomical term occultation ‘obscuring of one celestial body by another’ [16].

The modern associations with supernatural mysteries did not begin to emerge until the 17th century.
=> cell, conceal, hall, hell[occult etymology, occult origin, 英语词源]
occult (adj.)youdaoicibaDictYouDict
1530s, "secret, not divulged," from Middle French occulte and directly from Latin occultus "hidden, concealed, secret," past participle of occulere "cover over, conceal," from ob "over" (see ob-) + a verb related to celare "to hide," from PIE root *kel- (2) "to cover, conceal" (see cell). Meaning "not apprehended by the mind, beyond the range of understanding" is from 1540s. The association with the supernatural sciences (magic, alchemy, astrology, etc.) dates from 1630s.