Passover surname

Hi

I am doing some family research and have found out that my Great Grandmother x 2 was a Susan Passover and that she had a sister called Hannah. Both were born in Norfolk England in the late 1700 early 1800's. Can anyone tell me is it likely that they had a Jewish heritage and would it be likely that if they had that they would have "married out" at that time? Can anyone suggest where I take my research from here?

Thank you
B