My great grandmother, Alice Bunnager, consistently spelled her name with the "er" ending, but most surviving members of the family use the "ar" ending.
I have researched this family back to the mid 1700s and I have found the following spellings:
Bonigar
Bunegar
Bunnegar
Bunnagar
At one point, one son in the family, Thomas, born in 1824, started ending his name with an "l" and the following varients have continued into modern times. These varients include:
Bonnigale
Bonnigal
Bonegal
Bonigal
Although Bunnagar is an unusual name and should be easy to find in a search, the varients do confuse things!