ecstasy (n.) Look up ecstasy at Dictionary.com
late 14c., "in a frenzy or stupor, fearful, excited," from Old French estaise "ecstasy, rapture," from Late Latin extasis, from Greek ekstasis "entrancement, astonishment; any displacement," in New Testament "a trance," from existanai "displace, put out of place," also "drive out of one's mind" (existanai phrenon), from ek "out" (see ex-) + histanai "to place, cause to stand," from PIE root *sta- "to stand" (see stet).

Used by 17c. mystical writers for "a state of rapture that stupefied the body while the soul contemplated divine things," which probably helped the meaning shift to "exalted state of good feeling" (1610s). Slang use for the drug 3,4-methylendioxymethamphetamine dates from 1985.