Where does the saying daft as a brush come from?

Answer 1

Actually the full expression is: Daft as a brush and not half as useful. In the days of chimney sweeps children were often used to clean chimnies as they were the only ones small enough to access the chimney to sweep it out. They were held upside down inside the chimney and accidents frequently ensued resulting, of course in brain injury. Hence the expression "daft" which means silly, unable to concentrate etc.