English idiom, meaning "silly" or "excitable"
"Barmy is as barmy does" - Northern English expression
Barmy. Oh, boy, do I feel like that right now. Having created a nodeshell yesterday with the intention of filling it tonight, I returned to find it well-populated with excellent writing. "It should have been me!" was my first bitter cry - my thunder stolen, I sat awhile and licked my wounds, before /msging the author of the first write-up therein to congratulate him on a deservedly C!'d article.
"Barmy" comes from the old English word barm, meaning "yeast". According to my grandfather, it was used to describe bakers who had eaten uncooked bread dough, and became tipsy. A second meaning has to do with exuberance, and again this is down to the behaviour of the yeast, which left to its own devices in a warm, sugary solution, produces vigorous bubbles. It is still used, most especially in the Midlands and North of England, to describe someone whose behaviour is, shall we say, odd or eccentric.
"Barm loaf" is a spicy fruit bread once popular in the Midlands and North of England. Brits should think of malt loaf like Soreen.
Alternative spellings abound, notably balmy, but that's to do with balm, a totally different kettle of, um, fish.