And here, we used to say: St. Stephen, a 9th century Swedish missionary, is the patron saint of horses.

Further research, and a kind note from Pastor Philip A. Gardner of Lancaster, Ohio, reveals that the Boxing Day St. Stephen has in fact nothing at all to do with Sweden or with horses.  The Stephen for whom the day is named is the one in the Bible (Acts 6-8) who was the first Christian to be martyred for his faith.