Question: What's the origin of the expression "let the cat out of the bag"?
Answer: Our sources offer several theories to explain this colorful phrase, which means "to give away a secret." One story claims that the phrase originally referred to the moment when an officer aboard a British ship, preparing to administer discipline to some unfortunate sailor, would take a cat-o'-nine-tails out of its carrying bag.
Another story, which several sources repeat, claims that small pigs were at one time sold in bags, and an occasional unscrupulous merchant would put a cat in the bag instead of a piglet. When the bag was opened, the scam was revealed.
It may seem strange that pigs might once have been sold sight unseen in bags, but our sources offer two explanations for this practice. One is that the small pigs were easy to carry to country markets slung over the shoulder (these bags were called "pokes," thus leading to the expression "a pig in a poke"). The unscrupulous seller would try to sell the supposed pig without opening the bag, using the excuse that the pig would be too hard to recapture should it escape.
An alternative explanation for the selling of pigs in bags is that such transactions occurred in Islamic territory, where it was illegal to sell pork because it was considered unclean. Some farmers continued to raise pigs secretly, according to this theory, and would sell them under cover of darkness hidden in easy-to-carry sacks. Again, dishonest merchants supposedly replaced pigs with cats.
As is often the case, our sources offer no solid proof of the truth of any of their stories. The supposed connection between a cat-o'-nine-tails being taken out of a sack and a secret being revealed seems especially tenuous and can safely be regarded as a fabrication. We do know, on the other hand, that pigs were indeed carried in sacks, but we have no evidence that they were ever replaced with cats.
Question: I've always been puzzled by the expression "the powers that be." Shouldn't we be saying "the powers that are"? Why do we phrase it this way?
Answer: Many set phrases sound odd to the modern ear, often because they originated hundreds of years ago and have not been changed. "The powers that be" is one such phrase. It can be found in the King James Version of the Bible at Romans 13:1. The full passage reads: "Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God." Today, we use the phrase to refer to those often unidentified persons who exert power or control over our lives.
Question: It bothers me when people use "expect" to mean "suppose" or "think" in sentences like "I expect you were sorry to hear that." It seems to me that we can't "expect" backwards in time - "expect" means "to look forward."
Answer: Criticism of the "suppose" sense of "expect" dates back to the last century, although the sense is actually much older than that (going back all the way to the 1500s). Many commentators have echoed your opinion rather vehemently.
Your point about "expecting backwards" has not been much propounded in recent decades, although we still hear it occasionally. These days, most handbooks on usage are content to dismiss the "suppose" sense of "expect" as "colloquial." Our evidence gives some support to that characterization, but only if "colloquial" is understood as meaning "characteristic of informal conversation" rather than as a term of disparagement. When "expect" means "suppose," it is almost invariably used with "I," as in your example, and it therefore appears most often in speech and in the kinds of writing that make use of the first person - correspondence, dialogue and informal prose.