I have quite a lot with Surnames as a middle name. One set of g-g-grandparents gave ten of their eleven children Surnames as middle names, those of various people who married into the family, only my great grandmother had two normal names Sarah Ann. It seems to be quite common in Kent.
Sometimes middle Surnames are those of notable local people, employers or benefactors. You will also find children given the names of battles, very popular after the Boer War.