The diction of mental instability is rich indeed. Already NOOBs has covered daft, nutter, and mad; now comes barmy. The etymology is interesting. From the mid-nineteenth century through the early twentieth, the adjective balmy was commonly used to mean (in the OED’s words), “weak-minded, idiotic.” In due time, this combined in the public mind with barmy, an obscure term derived from barm, that is, “the froth that forms on the top of fermenting malt liquors,” which had been metaphorically, but sparingly, used to mean “flighty” or “excited.”
By 1896, the confusion about the two words was such that a writer in the Westminster Gazette asked, “Should not ‘balmy’ be ‘barmy’? I have known a person of weak intellect called ‘Barmy Billy’.‥ The prisoner‥meant to simulate semi-idiocy, or ‘barminess’, not ‘balminess’.” As he suggested, barmy has since prevailed, no doubt in part to the felicitous barmy army, used to refer to political factions or supporters (a NOOB?) of particular teams.
The weak spot, whose center is off the coast of Brazil, is called the South Atlantic Anomaly, or S.A.A., and it has created a Bermuda triangle of space science. Under its influence, spacecraft can go barmy, losing data, having computer upsets and seeing ghostly images where none exist. (New York Times, June 5, 1990)/Our colleague Ron Charles checks in with Shakespeare scholars, who say Roland Emmerich’s “Anonymous” theory is half-snobby, half-barmy. (Washington Post, October 31, 2011)