Origin and history of brain-wave

"soft, grayish mass filling the cranial cavity of a vertebrate," in the broadest sense, "organ of consciousness and the mind," Old English brægen "brain," from Proto-Germanic *bragnan (source also of Middle Low German bregen, Old Frisian and Dutch brein), a word of uncertain origin, perhaps from PIE root *mregh-m(n)o- "skull, brain" (source also of Greek brekhmos "front part of the skull, top of the head").

But Liberman writes that brain "has no established cognates outside West Germanic" and is not connected to the Greek word. More probably, he writes, its etymon is PIE *bhragno "something broken."

The custom of using the plural to refer to the substance (literal or figurative), as opposed to the organ, dates from 16c. The figurative sense of "intellectual power" is from late 14c.; the meaning "a clever person" is recorded by 1914.

To have something on the brain "be extremely eager for or interested in" is from 1862. Brain-fart "sudden loss of memory or train of thought; sudden inability to think logically" is by 1991 (brain-squirt is from 1650s as "feeble or abortive attempt at reasoning"). An Old English word for "head" was brægnloca, which might be translated as "brain locker." In Middle English, brainsick (Old English brægenseoc) meant "mad, addled."

"moving billow of water," 1520s (Tyndale), alteration (by influence of wave (v.)) of Middle English waw, waue, which is from Old English wagian "to move to and fro," from Proto-Germanic *wag- (source also of Old Saxon, Old High German wag, Old Frisian weg, Old Norse vagr "water in motion, wave, billow," Gothic wegs "tempest"), probably from PIE root *wegh- "to go, move."

The noun and the verb have both been somewhat confused with waive. The usual Old English word for "moving billow of water" was yð.

The meaning "motion to and from with the hand or a held object" is recorded from 1680s. The sense of "surface in the form of a ridge and trough" is by 1540s. The meaning "undulating line" is by 1660s.

Figuratively, in reference to a flood, rush, or influx of anything, by 1580s. Of forward movements among people in masses, it is recorded by 1852; in reference to public feeling, opinion, etc., by 1851.

Specific use in physics is from 1832, in reference to sound. Wave-front, "continuous line including all particles in the same phase" is by 1867.

In meteorology, in reference to an advancing movement of atmosphere (heat wave, etc.), from 1843. Of earthquakes by 1760. The figurative phrase make waves "cause trouble" is attested by 1959, probably from boating.

Our culture is a nice flat-bed boat in the middle of a serene lake of complacency; anyone who splashes or makes waves is immediately pinioned by the state, the church, and the indignant populace. [Daily Tar Heel, April 4, 1959]

"I'm in one canoe, you're in another, the captain's in a canoe, the colonel ... You know what you do when you complain to somebody or report somebody or request something? (Irvin shakes his head). You make waves." [Ronald D. Scofield column in Santa Barbara News-Press, Dec. 6, 1959]

The crowd stunt making a wave-like effect in stadiums is attested under this name from 1984, the thing itself said to have been done first Oct. 15, 1981, at the Yankees-A's AL championship series game in the Oakland Coliseum; soon picked up and popularized at University of Washington.