Strangely, Professor Moriarty and his brother have the same name.

Sherlock Holmes mentions his nemesis seven times in “The Final Problem,” but always as “Professor Moriarty” — he gives no first name (“My dear Watson, Professor Moriarty is not a man who lets the grass grow under his feet”).

But at one point Watson refers to “the recent letters in which Colonel James Moriarty defends the memory of his brother,” who was killed after his dramatic struggle with Holmes atop the Reichenbach Falls.

But in “The Adventure of the Empty House,” Holmes remarks to Watson, “[I]f I remember right, you had not heard the name of Professor James Moriarty, who had one of the great brains of the century.”

So “the Napoleon of crime” and his brother are both named James, it appears. One explanation that’s been suggested is that “James Moriarty” is a compound surname — in which case the first name of each man remains a mystery.