Though a Muggle village, Tinworth in Cornwall has been a place where wizarding families have congregated for hundreds of years, much like Godric’s Hollow and Ottery St. Catchpole (DH16). In the 1200s, famous Arithmancer Bridget Wenlock lived in Tinworth (BoS). Among the town’s current wizarding residents are Bill and Fleur Weasley, whose Shell Cottage home is on the outskirts of Tinworth on the coast (DH23).
Tinworth likely got its name from the fact that tin has been mined in Cornwall since prehistoric times.
From the Web
The best essay on the location of Tinworth/Shell Cottage to be found on the web is this one from madasafish.com.