Gnostic (n.)

1580s, "believer in a mystical religious doctrine of spiritual knowledge," from Late Latin Gnosticus "a Gnostic," from Late Greek Gnōstikos, noun use of adjective gnōstikos "knowing, able to discern, good at knowing," from gnōstos "known, to be known," from gignōskein "to learn, to come to know," from PIE root *gno- "to know." Applied to various early Christian sects that claimed direct personal knowledge beyond the Gospel or the Church hierarchy; they appeared in the first century A.D., flourished in the second, and were stamped out by the 6th.

"relating to knowledge," especially mystical or esoteric knowledge of spiritual things, 1650s, from Greek gnōstikos "knowing, good at knowing, able to discern," from gnōstos "known, perceived, understood," earlier gnōtos, from gignōskein "learn to know, come to know, perceive; discern, distinguish; observe, form a judgment," from PIE *gi-gno-sko-, reduplicated and suffixed form of root *gno- "to know."