Recently watched a documentary, 'What the Edwardian's Sounded Like,' in which they have German recordings of several British POWs from the First World War. One of the recordings was of a man from Macclesfield, near Manchester in England. He recites a biblical passage that frequently says 'father' but he pronounces it 'fay-thur' or 'faither.' I'm from Scotland and that is a well known and commonly used way to say father although I haven't heard any of the people I know from the North West of England use that expression that seemed to be common speech for the man being recorded!
Are there any examples of once common expressions being isolated to a single area over time? Or any other similar linguistic issues that have come about with the passage of time?
I’d bring to your consideration the example of the french language spoken in Québec. Initially founded as the colony of New France, the French spoken in the colony reflected mostly that of the regions of France from which the colonists originated – mostly in the north (Anjou, Poitou, Normandie, Bretagne). But after the Treaty of Paris, New France was ceded to the British and became isolated from France. The British mostly secured the peace by allowing the French colonists to retain their language, their culture and their catholic religion through the Québec Act of 1774 (it took them a while to figure out the benefits of this at first), just as contacts between France and the colony decreased, creating isolation.
In the meantime, back in Europe, the French revolution happened. At that time of upheaval, the French language as spoken in Europe shifted to align itself on the standard pronunciation of the Parisian Bourgeoisie. This shift was not reflected in the language of Québec, which retained a lot of its langue d’Oïl roots, and pronunciation, terms and expressions rooted in the Saintongeois, Breton, Picard and Normand dialects of its founding families.
To this day, the linguistic divergence between Québec French and continental French is a subject of fascination, interest and at times amusement when we meet with our estranged cousins from across the ocean.
Examples of the survivance of old local words and expressions in Québec include:
barrer une porte (lock a door) - our French cousins would say “verrouiller une porte”;
gosser as opposed to "tailler" (to sculpt wood with a knife – or whittle);
garrocher (to throw) instead of “lancer”
For more info and a deeper look into the linguistic peculiarities and the preservation of terms & expressions in Québec now disappeared from France, you may check into:
http://thecanadianencyclopedia.ca/en/article/french-language/
Plourde, Michel and Pierre Georgeault, ed. (2008). The French Language in Quebec: 400 Years of History and Life