Where does the name Musther come from?

It is thought to have come from Europe, named after the occupation of mustard sellers, who settled in Scotland, and over the centuries migrated down to North East England. During the 1700's & early 1800's many Musthers lived along the River Tees, in Yorkshire. The Mustards are also found in this area. On the Family Search IGI Musthers are found living in Switerland.