I have been making a survey of unusual names for nether undergarments. My interest in this subject was sparked off by an instruction given to me the other day by a kindly nurse when I went to our local hospital for a small test: "Push your bangers down to your knees", she said; I guessed at once what she meant and complied. I then asked her what the derivation of this colourful term was; she told me that in her family that was what they always called them, and seemed surprised that this usage was unfamiliar to me, and, as I later discovered, to everyone else I know.
And the OED appears to be unaware of them. Under banger it gives: he who or that which bangs; an astounding lie; a bludgeon (U.S. slang, at Yale); a violent kiss; a sausage; an old motor vehicle; and a banjo (obsolete). Partridge's Dictionary of Slang has most of these plus, in the plural, testicles; I'm glad I didn't know this before, I might have misunderstood the nurse.
Both sources make no mention of underpants, so I might suppose that the term is used for these only within the nurse's family, but I will probably be told by some know-all that it is common currency in the East End of London, in the Gorbals, or in Sydney.
Before another test, later, I was offered a pair of huge blue things which they told me are known as Dignity Pants. I suppose they meant well, but this is a misnomer; I didn't bother to ask "Does my bum look big in this?" because I knew what the answer would be. Still, I suppose the intention is good; most hospital garments are designed to humiliate you and I am doubtful about the rumour that Armani has been commissioned by the NHS to create a new range of gowns.
In the army, Quartermaster's Stores used to issue large white things called Drawers, Cellular. I have no idea why this piece of information has stayed in my memory.
And finally, there are the voluminous things worn by ladies of a certain age and size; they might be called Widdecombes, but to the pious they are known as Harvest Festivals. I believe this comes from a line in the Harvest Hymn: All is safely gathered in.