kthn tkhn khtn hktn thkn htkn ktnh tknh knth nkth tnkh ntkh khnt hknt knht nkht hnkt nhkt thnk htnk tnhk nthk hntk nhtk
Note: these 'words' (valid or invalid) are all the permutations of the word kthn. These words are obtained by scrambling the letters in kthn.