1580s, "believer in a mystical religious doctrine of spiritual knowledge," from Late Latin Gnosticus "a Gnostic," from Late Greek Gnostikos, noun use of adjective gnostikos "knowing, able to discern, good at knowing," from gnostos "known, to be known," from gignoskein "to learn, to come to know" (see gnostic (adj.)). 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 gnostikos "knowing, good at knowing, able to discern," from gnostos "known, perceived, understood," earlier gnotos, from gignoskein "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" (see know (v.)).
