The Oxford Names Companion, OUP "Scottish Forenames" - Donald Whyte, FGH, FSG Chambers Dictionary [2003]
Notes:
English either from Latin "yielding to prayer" [Whyte] or, possibly but (?) less likely, from a spelling variant of Anabella [ONC] or Amabel [Chambers].
Thanks to Donald Whyte who provided much of the initial information for this site.