English is a living, constantly evolving language. It was altered by Roman Catholic missionaries who brought their Latin mainly in the eighth century. Around the ninth century, the Vikings took over the north and east of England and many old norse and Danish words changed English. Given they were Vikings, it is no wonder that they gave us words like get, take, die, anger, nay. Thanks a lot. Then the Normans altered the language starting in the eleventh century. Their also conquerer status tells in English as the English would be recognized as slaves to the Normans by our modern notions. For example, an Englishman tended to pigs, but the finer cuts went to the Norman masters. So swine and bacon (the opposite of living high on the hog, and least desirable and therfore, fit only for an Englishman) were English words. The finished product, mutton is Norman French. Perhaps we should dump all this foreign drival and go back to real English. In my view, the same fate can await this idiotic alphabet and insane spelling. I am certain the old English spelling and alphabet is far superior. But I digress.
I invite twenty-first century speakers of English to visit web sites that have audible files of phrases spoken in the original English. You will conclude that the language is essentially completely changed. Therefore, let us go back to German and old English to understand what a Chapman is. We have a counterpart in German people whose surname is Kaufman. It is derived from the old high German word 'chouph'. The old English had several words of similar meaning. 'Cop' meant barter. "Chipping' was a place where things were bought. 'Ceapian' meant to buy. The old English word 'ceap', also meaning barter, mutated into our modern word cheap. More telling is the old English word 'Ceapman' the old word for a pedlar or merchant, and were usually traveling merchants moving from village to village. So our ancestors were named for their occupation of traveling merchant. There are other examples of occupational surnames such as Smith, Baker etc. It mattered not what specific goods they sold, they were Chapmans.