Hrmmm. Variations of Black Pudding exist in other countries outside of the British Isles. In Spain, "morcilla" is a similar blood sausage, often made with rice or onion. France has "boudin noir," which also features blood and fat but varies in spices and preparation. Italy has “sanguinaccio”, among other things. Black Pudding is actually quite universal.
I’d say in a British Isles context, Lancashire, England and the Western Isles of Scotland have long histories of making Black pudding. Lancashire black pudding is characterized by its unique blend of spices and texture, likely because of Lancashire’s maritime location, with important sea ports, importing spices from far-flung places, as is the case with the Cumberland sausage. If i’m not mistaken, the history of Black Pudding in Lancashire goes back to the 14th century, and underwent major changes in the 18th and 19th century during the Industrial Revolution when it became a staple food.
Black Pudding, particularly from the Isle of Lewis in Scotland, has a rich history rooted in local traditions and the island's unique cultural heritage. If my memory serves me correctly, Western Isles black pudding dates back several centuries, with roots tracing as far back as the 16th century.
The Netherlands have a black pudding too called ‘bloedworst’, which translates to blood sausage. I’ve seen it in the supermarket but I have yet to try it.
One of the courses I followed at university was ‘culinary history’, it was part of my Master’s degree in History. It peaked my interest in everything culinary.