A British slang expression, meaning 'nothing at all' or 'next to nothing'. What, you ask, does the FA stand for? Well, that is a subject of some debate. Most regard the FA as standing for 'fuck all', which makes a certain amount of sense. However, a more fun explanation has been proposed. In 1820, a young lady from Hampshire was murdered and hacked into little bits. Her name was Fanny Adams. Coincidentally, at about the same time, the Royal Navy was experimenting with a marvel of modern technology- the tin can. Placed in said can was stewed mutton of a truly horrid quality, which was then fed to Royal Navy sailors.
How do the two relate? The story goes that a young sailor discovered a button from a woman's coat in with his meal, and claimed to his shipmates that he was being served little bits of 'sweet Fanny Adams'. The phrase stuck, as horrible, gory, things tend to do in human language, and in time was shortened to the abbreviated 'sweet FA'. Originally, it is thought to have meant 'something of terrible quality', but as the phrase evolved it arrived at its present meaning.