I've been meaning to get around to this for sime time and finally got off my duff.

The be- prefix in Old English had three possible meanings.

Quoted from A Guide to Old English by Bruce Mitchell and Fred C. Robinson:

be-      1  In some words be- is the same as the prep. 'about', e.g. be-gan'surround' and be-ridan 'ride 
              around, surround'.

          2  Sometimes it is a deprivative, e.g. be-dælan 'deprive' and be-heafdian 'behead'.

          3  It can make an intransitive verb transitive, e.g. be-<THORN>encan 'think about' and be-wepan 'bewail'.