To my knowledge, it's not just Annabel
with an M, it actually IS Annabel
with an M. Back in the merry Middle Ages someone in Scotland wrote Amabel
(good Latin name, meaning Lovable) and someone else misread the M as NN.
Short A in front is the pronunciation I know - like Annabel
, as you said. The only other attempt I've ever encountered was a sad effort to make it sound like aMAYbel, presumably because the name Mabel
is in there ...
looks as if it means Beautiful Anne
, but it originally meant Lovable. Trivia, but hey, trivia's fun!