London Particular

This question has got itself a bit back to front.

The original London Particulars were the fogs that used to form in the city during the 19th century, and well into the 20th. The fogs were also known as 'pea soupers', and this is how pea soup came to be known as London Particular - "in a reversal of the idiom", in the words of Wikipedia. In other words: the fogs were named after the soup, but they already had another nickname, and that got transferred back to the soup.