>How about expression, that russians use very often: "Prishla beda - otvoryai vorota"? (literally, when trouble comes, open the gate)

I've seen questions about origins of some proverbs, where some words are used of which nobody nowadays knows the meaning. On some forums, there may be a few people who have heard, or remember some other contexts, from older people - so some detective work sometimes yields interesting results. However, in some cases, nobody knows why do we say this or that, or what do those words actually mean.