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".
Incidentally, that word diverts my mind to a point that's always been a small fascination in language learning: the question of where to group similar things/concepts into a single word, and where to divide them into multiple words. Studying a foreign language brings home just what an arbitrary decision it always is, and how a single word in your own language might be broken into many finely nuanced words in a foreign language – or vice versa.
It's always a challenge when the foreign language offers finer distinctions. For instance, simply inquiring about someone's sister requires more information in some languages; in Japanese, you need to know whether to ask about an onee-san (older sister) or imouto (younger sister). In French, it seems awfully convenient that the English cousin remains cousin – except that you need to remember to use cousine for a female cousin. And I'd always heard that in Spanish, you needed to use very different words for dog and small dog – though attempting to verify that online now, I'm only finding a small difference, perro vs perrito. (Anyone know whether that's right?)
Going the other way, a dog is a dog in English, but an undefined line of size divides mouse from rat. Japanese also offers a special word for the bigger critter, dobunezumi, though that's still just a variant of nezumi (mouse), not a whole other word as in English. Or another example from Japanese: hazukashii can equally mean embarrassed or shy, with no commonly-used words to offer the finer distinction that the English words make (other than, perhaps, hazukashigariya, a noun indicating a shy person). And, of course, the plural case offers a fine example of a distinction that isn't universal. You need to always count (is there one of a thing or not one of the thing?) when you go from a language without plurals to a language that does use those pesky things. (That pesky thing?)
That takes me back to chuudoku and the its embracing of two (English-language) distinctions. It's used for both poisoning (as in lead poisoning en-chuudoku 鉛中毒 or food poisoning shoku-chuudoku 食中毒), and for addiction (as in drug addiction mayaku-chuudoku 麻薬中毒 or alcohol addiction / alcoholism arukooru-chuudoku アルコール中毒). While it's certainly economical for a language to go broad with concepts like this, here we see an example of a case in which a foreign speaker might feel the conflation to be overdone. That is, yes, both addiction and poisoning can clearly result from the mayaku-chuudoku of snorted white powder. But by the same token, shoku-chuudoku could refer to both food poisoning and food addiction. The actual meaning covers only the former danger, leaving the latter woe to search for an alternate word to call its own. (Hmm, shoku-izonshou 食依存症, food dependency, perhaps?)
Of course, in real life, context (and plain old memory of words' standard meanings) make clear whether a chuudoku is an addiction, a poisoning, or some of both; speakers of Japanese learn what shoku-chuudoku means and doesn't mean, and communication proceeds without trouble. All I'm doing in this little tangent, really, is pointing out a pleasant chuudoku that awaits many language learners: the addiction of subjecting newly-learned words and usages to comparison with one's native tongue, and maybe even musing about how the words and usages would work in a hypothetical "perfectly logical" language. One with really clever mechanisms for constructing words, so that you could equally group concepts into broad categories, or divide them into detailed words for fine subcategories...
Ahem. A universally agreed-upon "logical language" sounds both impossible and unnecessary. Human tongues don't much hew to such prescriptive logic, nor do they need to. Each one is a massive mess of handed-down arbitrary decisions made by who-known-who, back in who-knows-when. We may never know what decisions led to a language lumping this thing and that thing into one broad word, while chopping up those things into a dozen nuanced words. But I've always found it fun to play with the (wonderfully) illogical results.
End tangent. Back to work!