Based on the research I've done, the origin of the word vicambulist is described:
A vicus is simply a street in a town, whereas a vicarius (lying behind the word vicar) is a substitute. In fact, a vicus is a village, or group of dwellings. It is the smallest unit of ancient Roman municipal administration. From Stubb's 1874 Constitutional History of England: "The unit of the constitutional machinery in Anglo-Saxon England was the township, the villata, or vicus." So, a person who is a vicambulist "walks around" the town.