brain-coral (n.)

"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), 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. Figurative sense of "intellectual power" is from late 14c.; meaning "a clever person" is first recorded 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."

general name for the hard, calcareous skeleton excreted by certain marine polyps, c. 1300, from Old French coral (12c., Modern French corail), from Latin corallium, from Greek korallion, a word perhaps of Semitic origin (compare Hebrew goral "small pebble," Arabic garal "small stone").

Originally especially the red variety found in the Mediterranean, used ornamentally, hence "red, the (red) color of coral" (mid-15c.). As an adjective, "made of coral," mid-15c. The coral-snake (1760) is so called for the red zones in its markings. Coral-reef is attested from 1745 (see reef (n.1)).