Just a hint: Google gives 9,220 hits on "Greyfriar's Bobby" (with an apostrophe) and 97,000 hits on "Greyfriars Bobby" (no apostrophe).

Wikipedia says Greyfriars Bobby was a Skye Terrier, and was buried in churchyard of Greyfriars Kirk.

So I suppose that means the dog was known only as Bobby, at least while his master was alive, and became known as Greyfriars Bobby afterwards?