khud hkud kuhd ukhd hukd uhkd khdu hkdu kdhu dkhu hdku dhku kudh ukdh kduh dkuh udkh dukh hudk uhdk hduk dhuk udhk duhk
Note: these 'words' (valid or invalid) are all the permutations of the word khud. These words are obtained by scrambling the letters in khud.