Playing it Close to One's Chest
IDIOMATIC EXPRESSION DEFINITIONS
When we have a secret, sometimes we let it fly free like the ancient wax flyers of Greece. If the secret is hot, we will ignorantly soar high into the sky, melting the trust of our friends and falling to earth a sad and lonesome figure--likely a dead figure due the damaging impact. Not all secrets are so saucy as to tempt us with infidelity and not all infidels are saucy-mouthed assholes. No, there exists an older father-figure who makes sure his wax wings stay only marginally elevated and far from the burning sun. These dads keep secrets close to their chest. Dads often keep plans, knowledge, and their heart, close to their chest.
Playing it close to one's chest.
Keeping your intended actions or knowledge private.
When I started researching this idiom, I had a suspicion that it was a saying from the Medieval days of keeping valuables in a treasure chest. Along this note, I wouldn't have been surprised if it actually was from the piracy period either--since pirate's loved burying chests of treasure (jk: I've read many times pirates didn't care about retirement and instead immediately spent their loot).
It turns out, in fact, that the saying originated around a game of cards. These card playing, gambling, stone-faced/poker-faced, raw-doggin' pawns of the devil loved to be the only ones who knew what their cards were. Playing cards is a lot like taking a test. Only the highest score gets the love and affection from Teacher. In poker, only the best hand of cards wins the prize money. There is no second place.
Player's of the card game assemble around a circular table, so that they can face one another. World leader's or Executive's of a business often use the same tactic. Therefore, holding your cards to face either the left or the right will be a dead giveaway of which cards you have received from the dealer. This tell will be your undoing, as other players will know if there standing in comparison to your hand. The most logical way to hold cards is close to the player's chest, but not as close so not to see them.
I am really disappointed that the idiom didn't get its history from keeping secrets close to the treasure chest. Of course, I suppose that if you were to actually need them protected, you would open up the chest, put the item inside, and then close the lid again--potential even locking it shut. Please don't keep this idiom close to your chest, though, use it as often as possible, up to 5 times in any given conversation.