Barking/Barking mad

Barking mad means extremely mad, where barking is used as an intensifier. Barking, however, is sometimes used on its own, and a person who is described as 'barking' is simply mad. The OED's entry for barking contains no reference to mad, but states that barking means 'harsh coughing' and cites this from 1813. Then, confusingly, it gives a figurative meaning of barking as 'an angry outcry' and dates this from 1549! We have it on good authority that the OED is currently revising its entry for 'barking'. Michael Quinion on his website worldwide words gives a first citation for 'barking mad' from the 1930s, but there is evidence that it is very much older than this. In a letter to the London Chronicle dated October 1760, a doctor, writing about cures for rabies used the phrase 'barking mad' to describe the effect of rabies on someone who had been bitten by a rabid dog. Therefore, it seems reasonable to suppose that the origin of 'barking mad' derives from the madness that rabies inflicts on people who get bitten by rabid dogs. Some sources claim that 'barking mad' is also British rhyming slang for bad, 'barking mad/bad', but to our knowledge it does not appear in any dictionaries or compendia of rhyming slang. For example, there are three entries for 'bad' in Ian Hall's Comprehensive Dictionary of Cockney Rhyming Slang published in 2018, Alan Ladd/bad, Shepherd's Plaid/bad, and Sorry and Sad/bad, but nothing for Barking mad. It could be the case that barking mad/bad has verbal usage but has not yet appeared in credible print, correspondence, or broadcast media. If and when it does, of course, it will be given due recognition. Until the OED publishes its revisions for 'barking' to include 'barking mad', the exact date of origin is best left in abeyance, but thus far, the 1760 claim in the London Chronicle holds the field. See also My dogs are barking.