[Facts] Re: Male names for Female
If the name was one of the most popular male names (e.g. John, William, James, etc.) then it almost always showed up on the female list as well, and vice versa. Names with that much usage naturally had the most coding errors, especially in earlier years, adding up to enough to make it appear on the list.
When an uncommon male name shows up on the female list, it probably was being used for girls.