Boswarthack or Boswarthick is a surname that I haven’t yet covered in either book or blog. It comes from a place in Constantine parish spelt Boswodek in 1330 and Bosvathek in 1519. This apparently meant a settlement by a water-course or stream.
In the 1500s the distribution of the name Bosvathek (also spelt occasionally Boswathek) mostly clustered around its point of origin.
It began to be spelt with an <r> as early as the 1580s and this had taken over as the predominant spelling by the 1700s. There were still quite a few families with this surname, as the map below indicates. Yet, by the 1861 census, only two household heads called Boswarthick remained (at Stithians and Perranarworthal – both quite close to its point of origin.)
For contrast, here’s a map of the surname Polglase, a locative name with multiple origins. For a map of Polglase in 1861 see here.