A potential answer from communication with the volunteer for this parish at Cornwall Online Parish Clerks: 'Barah' is likely a small farm adjacent to Headon Barrow in Jacobstow parish. The barrow itself is a prehistoric burial ground, which are quite common in Cornwall, but according to the 'online parish clerk', _barrow_ would have been pronounced and heard as _barah_ by a local Cornish person in 1826. The farm today is known as South Headon, but it is unnamed on the 1883 ordnance survey map available from the National Library of Scotland <
It seems a bit stretchy, but this appears to be the only barrow in this parish, so the farm may have been known at the time by its proximity to this well-known landmark.