Rhyming slang for hair, Barnet Fair/hair. It is one of the oldest examples of rhyming slang, first recorded in 1857. By 1880, its ‘clipped’ form ‘Barnet’ was in use. There has been a horse and livestock fair at Barnet since 1588, when it was granted a royal charter in the reign of Elizabeth I. It is held annually for three days starting on the first Monday in September. These days it is simply a fun fair with no livestock on show.