In addition to placenames in Wales being in Welsh or having Welsh equivalents of their English names, there are also words in Welsh for some towns, cities and counties elsewhere in the British Isles. For English counties, the Welsh names for their county towns are often prefixed by the Welsh word "Swydd", meaning an English shire or county, to produce the comparable word in Welsh for the county itself (the Welsh word "Sir" means a Welsh shire or county).

There is a list on the 1911 Census web site and on Findmypast's Knowledge Base for the 1911 census of the Birthplace Codes that the census clerks added to the Household schedules for analysis purposes. These distinguish betwen the counties in the case of Scotland and Ireland, but for England the codes go down to the larger towns and cities, and the various districts within London. The numerical code that has been added may therefore help when trying to decipher ambiguous handwriting