Arabella according to nameberry means yielding to prayer but behind the name says it is a medieval Scottish name possibly related to Annabel (meaning through Amabel, loveable). Arabella is a fast rising name in the UK and the US, in the UK it is in the top 200 at 157 up 20 places from last year. In the US it was given to 1512 babies up 204 babies currently at 210. In Victoria in 2012 it was at 204. I do know an Arabella though her name is spelt Eirabella, said as Arabella.
One problem many people have with Arabella is it’s too over the top or sounds like an Arab named Ella. Though I pronounce the name Arr-ah-bell-ah and Isabella is a top 20 name (at 11 in Australia). Will Arabella rise to the top 200 in the US and Australia and the top 150 in the UK? Most likely yes since its not a meteoric rise needed (only 10 spots and could be in the top 200 in Victoria I just have no way of knowing).