Another good bit from the Etymologicon [previously]. This time, why brackets are named after codpieces. The ever-more-elaborate codpieces in medieval armour were called braguettes.
A Braguette
Then came an architect fixated on groins
What do you call the bit of stone that bulges out from a pillar to support a balcony or a roo? Until the sixteenth century nobody had been certain what to call them; but one day somebody must have been gazing at a cathedral wall and, in a moment of sudden clarity, realised that the architectural supports looked like nothing so much as Henry VIII’s groin.
So the supports became known as braguettes, which first became brackets in a dictionary compiled by Pocahontas’ lover. Then, because a double bracket looks a bit like [, the word was transferred onwards to name a piece of punctuation