Why is fayre spelled differently to fair?
That's probably the Old-English (anglo-saxon language) spelling.
There is actually no way to say Courtney in Spanish... many names in English are spelled the same, and only pronounced differently in Spanish. Some names are pronounced and spelled differently in Spanish but Courtney just isn't one of them. One example of a name that is spelled and pronounced differently is Andrew, in Spanish it's spelled Andres with an accent over the e.
A homophone is a word that is pronounced like another word, but is usually spelled differently. The words may be spelled the same, however, like rose and rose. Words that are spelled the same are called homographs and homonyms. If the words are spelled differently, the are also heterographs. A homophone for the word farrow could be Pharaoh, or Faro.