Thus perhaps, emerged a village known as Salisbury - a well-known placename in England and the home of Salisbury Cathedral, the church with the tallest spire in all of England. As families back then were identified by their work or their holdings, it well may be supposed that here the Salisbury family name had its roots. However, one must not overlook the existence of Salzburg, Germany. The Germanic peoples (Angles and Saxons), who invaded the island in the distant past may have mde their contribution toward the name.
Note: With nothing being known of William Salisbury I's forebears, it is difficult to nail much down -- after, the dude did live over a thousand years ago!