bock obck bcok cbok ocbk cobk bokc obkc bkoc kboc okbc kobc bcko cbko bkco kbco ckbo kcbo ockb cokb okcb kocb ckob kcob
Note: these 'words' (valid or invalid) are all the permutations of the word bock. These words are obtained by scrambling the letters in bock.