Searching the forums, just in case you aren't familiar: if you don't see the search box right at the top of the forum
thread list, there is a link to full search options at the top of every page (above the
video pic).
Short
answer is any users who had signed up under the old software without a last name were assigned 'Hatfield' or 'McCoy' until they update their user profile for a name change. See the thread on
using a real sounding name for why permies folks use first-name, last-name.