You just type in ??? in the search box, for three-letter names. Or ?? for those of two letters. Then you'll get a whole list of names of both lenghts.
And that goes for other lenghts. For a list of nine letter names, this is what you have to type in ?????????.
That was what I was told by Mike, once I asked about the same.
RIP: Don S. Davis
4 August 1942 - 29 June 2008
"Major General George Hammond - Stargate SG-1"
Nameblog: http://charliebnamed.blogspot.com/