“Дело – табак” (literally: the thing is the tobacco which can be translated in English by the goose is cooked). It means что всё плохо (that everything is wrong), irreparable. Some experts suggest that this expression могло появиться в среде бурлаков (might have appeared among barge haulers), that used to pulled barges on the rivers or in shallow water against the current, in places where a boat could not sail by itself.
Перед тем, как войти в воду (before entering into the water), бурлаки привязывали мешочки с табаком на шею (the barge haulers tied their tobacco bags around their neck), чтобы не намочить (so it wouldn't get wet). But if the bottom of the river suddenly got deeper, and the man who was pulling had water up to the neck and thus had his tobacco bag wet, it meant that двигаться дальше уже было невозможно и опасно (it was already impossible and dangerous to move further).
But scientists have other versions: since there are several similar expressions “дело дрянь” (rubbish, it is rotten) and “дело труба” (things are in a bad way) we can assume that “табак” and “труба” arose from the sound association of the word “требах”. This word that Russians could have heard from merchants from the East means “дрянь”(rubbish) when translated from Iranian.
Another idiom which has to to with important things which are kept close to your skin: “за душой ни гроша” (not a penny for my soul). It means as you might have guessed to have a total lack of money. Actually, money was often concealed close to the body, in a purse hanging from the neck deep between the clavicles which is also called “душой”. This expression meant a person had no money at all, not even hidden in the most secret place.
Дело – табак (literally: the thing is the tobacco which can be translated in English by the goose is cooked).