crazy (adj.)

1570s, "diseased, sickly" (a sense now obsolete); 1580s, "broken, impaired, full of cracks or flaws," from craze + -y (2). Meaning "deranged, demented, of unsound mind or behaving as so" is from 1610s. Jazz slang sense "cool, exciting" is attested by 1927. Related: Crazily; craziness.

To drive (someone) crazy is attested by 1873. To do something like crazy "with manic vigor or frequency" is by 1905. Phrase crazy like a fox has origins by 1935. Crazy Horse, name of the Teton Lakhota (Siouan) war leader (d. 1877), translates thašuka witko, literally "his horse is crazy." Crazy-quilt (1886) preserves the original "break to pieces" sense of craze (v.). Crazy bone as an alternative to funny bone is recorded by 1853.

Definitions of crazy
crazy (adj.)
affected with madness or insanity;
Synonyms: brainsick / demented / disturbed / mad / sick / unbalanced / unhinged
crazy (adj.)
foolish; totally unsound;
a crazy scheme
Synonyms: half-baked / screwball / softheaded
crazy (adj.)
possessed by inordinate excitement;
was crazy to try his new bicycle
the crowd went crazy
crazy (adj.)
bizarre or fantastic;
had a crazy dream
wore a crazy hat
crazy (adj.)
intensely enthusiastic about or preoccupied with;
crazy about cars and racing
Synonyms: wild / dotty / gaga
crazy (n.)
someone deranged and possibly dangerous;
Synonyms: loony / looney / nutcase / weirdo