Questioning correspondent B.W. is looking for a Japanese word meaning "a bad habit" and which he recalls as possibly tsudoku.
Neither my memory nor dictionary contain such a word, nor anything really close. (There's tsuudoku つうどく 通読, meaning to "read through [thoroughly]", but that's not it.)
My guess is that the word being sought is chuudoku ちゅうどく 中毒, which is "poisoning" or "addiction". The latter meaning might include that idea of "bad habit". Read more about What's that word?: Chuudoku (poisoning / addiction)