common as muck

Here's a sort of global version of the UK-only surname distribution tool - stick your surname in here and you'll get some indication of how prevalent it is worldwide. Now fairly obviously Thomas is a popular and widely-distributed name (the 264th-most-common surname in the world, apparently) but there are still some interesting nuggets that can be plucked out of the information provided:

• Thomas is the 4th-most-popular surname in Wales (only Jones, Davies and Williams rank above it), but only the 8th-most-popular in England, 99th in Scotland and 403rd in Ireland;
• It's well popular in the Caribbean, featuring in the top ten in Trinidad & Tobago, Guyana, Grenada, Antigua & Barbuda, Dominica, United States Virgin Islands and British Virgin Islands;
• You have to go a bit further south for the place with the most Thomases, proportionally speaking: Saint Helena, Ascension and Tristan da Cunha. Thomas is the most popular surname here, although as there are fewer than 10,000 people spread across the various islands that only amounts to a few hundred individuals, some of them possibly albatrosses;
• There are a few countries at the bottom of the list with only a single Thomas in the whole country. Comparing the "Frequency" and "Rank" numbers for these reveals some interesting variation in what you might call surname diversity in various countries. Have a look at the last three entries on the list, for instance:
  
  So Tajikistan and Burundi are about the same size, but apparently Tajikistan has 11,831 distinct surnames (if we assume that Thomas occupies last or joint-last place on the list), while Burundi has only 1,253. Even more remarkably, Mauritania, with only about a third of the population, has a whopping 38,063 distinct surnames. Similarly, San Marino appears to have many more distinct surnames than Eritrea, despite only having something like 5% of the population.

As for the other list, interesting contrasts can be provided by using my wife's unmarried name, Hannant, as input, since it's far more unusual (219,619th-most-common worldwide). Apparently there are 855 of them in England, but only one in Wales. Whether that's Hazel, her sister Paula, or some third party as yet unknown isn't clear.