Yes, Annieoburns,
The cause is never lost, especially with the internet to help us now...
I was also mistaken about BICHENO (pronounced with the emphasis on the first syllable, apparently), being perhaps of Mediterranean origin.
As it says on the Over website, it probably stems from the lost place from the Domesday Book called there Byccenho or Birchenhoe, meaning land with beech trees on it by a river, on the borders of Northants and Bucks. The river there is a tributary of the River Great Ouse, which today forms the northern border of Over parish...
keith