But even today, if people use the words of French origin rather than the old English words, one is regarded as being from the upper class, such as using 'purchase' instead of 'buy'.
https://en.wikipedia.org/wiki/List_of_English_words_of_Frenc...
https://en.m.wikipedia.org/wiki/High-_and_low-context_cultur...
This features quite a bit in War and Peace, too. As tensions increase between France and Russia as Napoleon takes over much of Europe and war between the countries looms, you'll find Russian nobility taking Russian language classes, because their first language is French!
Such as pig/pork, beef/cow. The working classes spoke English and dealt with the live animals, the elites just ate them.
But I don't think this is well explained by a class distinction. I mean, the classes of people who raised sheep weren't so different from the people who raised chickens.
Pheasant: from Old French fesan. (the current french is faisan).
Upper class: valet [val-ett], fillet [fill-ett]. Middle class or lower: valet [val-ay], fillet [fill-ay].
Upper class: claret [clar-ett] (from French clairet). Middle class or lower: Bordeaux.
https://en.wikipedia.org/wiki/Sociolect
Basically, since class is culture, and cultures have language, a sociolect describes the language of a class, the ways you have to talk to perform that class.
And, naturally, this goes both ways. Someone talking the sociolect of a certain class is seen as performing that class, and therefore belonging to the class.
It should also be noted that the original article is itself a class performance! The author uses more complex words and grammar than necessary, thereby signalling academia or professional class. (Someone in the comments on that page wondered why this article had a more complex language compared to other articles by the same author, but didn't connect the dots...)