Fickleheaded, blackballed, and blackmailed share a peculiar property. Similarly soupspoons, topsy-turvy, and nonsupport share a related but not identical property.
What are the two properties exhibited by these groups of words?
Each of the three words in the first group - that is, "fickleheaded", "blackballed" and "blackmailed" is entirely constituted by the first half of the letters in the alphabet, that is - the letters A to M.
Each of the three words in the second group - that is, "soupspoons", "topsy-turvy"(disregarding the hyphen) and "nonsupport" is entirely constituted by the second half of the letters in the alphabet - that is the letters N to Z.