Welcome to rootschat Heritagefound.

Surnames as middle names happen everywhere. I am not sure you can glean anything from it regarding denomination or geography. In my research I have observed it is particularly common in the NE and Scotland.
Sometimes the surname can be passed down from an earlier generation which you may not be aware of as yet, a maternal surname for example, sometimes it could be a way for a family to honour employers, neighbours or friends or someone of esteem in the community.
I have told this story many times, but as you are new, I will repeat it.

The father one of the families I was researching wrote a diary and in it he detailed how he chose the middle names for his children including bestowing the surname of “someone who was kind to his wife” on one of his children. In each case he requested that those surnames be passed down the generations. (They weren’t.

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If you haven’t already done so, it might be worth looking in the censuses for people with these surnames living near or working in the same trades as your ancestors. You may find a connection with some of the more unusual surnames - there may be too many results for the common names.