The surname Smith is very common in the British Isles. It likely derives from the Old English word 'Smid', which means to strike, and was used to describe an individual who worked with metal. Hence where the occupational terms 'blacksmith', or 'silversmith' came from. The name is so common today because in the past, each settlement would have had a smithy. So when hereditary surnames started being used, the surname spread quickly. 

Variations include Smithe, Smyth, Smythe, Smeeth, Smiths.

In the 1881 UK Census, Shetland is recorded as having the highest proportion of people with this surname.