A freak chance led to the revelation of Orabella’s hidden talents. In 1754, two of Europe’s most celebrated broom fliers ... agreed to a public broom race from Aberdeen to Rome ... Orabella was invited along to oversee the luggage and arrange the Portkeys.
-- Miranda Goshawk, describing the origin of the Reparo spell (BoS)
Aberdeen is a city of about 100,000 people on the eastern coast of Scotland, about 85 miles northeast of Hogwarts.
Modesty Rabnott's sister Prudence lived in Aberdeen c. 1200s, according to a thirteenth-century letter on display in the Museum of Quidditch (QA4).
During Harry's first trip on the Knight Bus, the bus moved to Aberdeen abruptly, spilling his hot chocolate. In fact, all three of the Knight Bus's stops on that trip - along with the place Harry talked to Stan Shunpike about during the journey - began with the letter A (PA3).
In 1754, two rival broom fliers, Torquil MacTavish of Scotland and Silvio Astolfi of Italy, raced each other from Aberdeen to Rome (BoS).
Here's a place I'd love to ask Rowling about - though I'm not sure many fans would agree with its importance! It seems nearly impossible that all four places mentioned on the Knight Bus would start with A by mere coincidence. But if it's not just a coincidence, of course, then there has to be a reason for doing it - and I can't figure out what that might be either. *Sigh* I'll probably never know. Perhaps Rowling simply had an alphabetical list of city names she wanted to use and started at the top.