[alkonaut]

Nice. I tried a simpler method of only looking at the wikipedia table of overall letter frequency in dictionaries (not in 5 letter words) and the vowels are high, especially E and I followed by A. Then I checked the frequeny of starting letter and that is led by "S". So my guess for a 5 letter word became one with at least two vowels from E,I,A, starts with an S, and has the remaining two characters from the reasonably high frequency set (R, T, N, etc). My guess then was SIREN which has that property. Just out of curiosity, if you still have the output from your program, how bad was SIREN compared to SLATE?