- acid
- 1620s, from Fr. acide, from L. acidus "sour," adj. of state from acere "to be sour," from PIE base *ak- "sharp, pointed" (see acrid). Applied to intense colors from 1916. Slang meaning "LSD-25" first recorded 1966 (see LSD); acid rock (type played by or listen to by people using LSD) is also from 1966; acid house dance music style is 1988, probably from acid in the hallucinogenic sense + house "dance club DJ music style." Acid test is Amer.Eng., 1892, from the frontier days, when gold was distinguished from similar metals by application of nitric acid. Acid rain is first recorded 1859 in ref. to England. Adj. acidic is attested from 1877, originally in geology.
“When I was on acid I would see things that looked like beams of light, and I would hear things that sounded an awful lot like car horns.” [Mitch Hedberg, 1968-2005, U.S. stand-up comic]