(for the worse), abnormal" (cf. O.S. gimed "foolish," O.H.G. gimeit "foolish, vain, boastful," Goth. gamaiþs "crippled, wounded," O.N. meiða "to hurt, maim"), from intensive prefix *ga- + PIE *moito-, pp. of base *mei- "to change" (cf. L. mutare "to change," mutuus "done in exchange," migrare "to change one's place of residence;" see
mutable). Emerged in M.E. to replace the more usual O.E. word, wod (see
wood (adj.)). Sense of "beside oneself with excitement or enthusiasm" is from early 14c. Meaning "beside oneself with anger" is attested from c.1300, but deplored by Rev. John Witherspoon (1781) as an Americanism, and now competes in Amer.Eng. with
angry for this sense. Of dogs, "affected with rabies," from 1800. Phrase mad as a March hare is attested from 1520s, via notion of breeding season; mad as a hatter (1857) is said to be from erratic behavior caused by prolonged exposure to poison mercuric nitrate, used in making felt hats. Mad as a wet hen is from 1823. Mad money is attested from 1922; mad scientist is from 1940.
maddingaction of the obs. verb mad "to make insane," c.1300; now principally in the phrase far from the madding crowd, title of a novel by Hardy (1874), who lifted it from a line of Gray's "Elegy" (1749), which seems to echo a line from Drummond of Hawthornden from 1614.