"Well, we're in a real pickle now." It sounds quaint, but we know what it means: We're in a real spot of trouble. But when you step back and think about it, why do we say anything about pickles at all when we're in a jam? Where did this phrase come from?
Older Than Shakespeare
You're not wrong if you think being in a pickle sounds old-fashioned. The Oxford English Dictionary (OED) has the earliest-known written instance of this phrase as from 1562. Granted, it's early days for modern English, so it looks a little odd to us now, but the idea is there:
In this quote, the author John Heywood is saying that man is brittle, or frail, and that frailties pickle, or keep, like pickled foods do. Even the OED admits that this early example is a little weak. But in this quote from 1585 by John Fox in a sermon he gave on 2 Corinthians, the meaning is closer to how we use it today:
By nature, humans are in a pickle, which certainly feels correct most days. By 1711, we can easily identify how the author Richard Steele was feeling:
But Why Pickle?
Lots of people do think Shakespeare originated the phrase. He's the source of so many phrases we still use, it seems reasonable to think he's responsible for this one too. He did use it in "The Tempest":
Here, Shakespeare was using "pickle" to mean "drunk." Since you can preserve things in alcohol, it's not a far leap from one to the other. But it is kind of a leap from "drunk" to "pickle" to "seemingly inescapable problem."
One answer might come from England, where "pickle" can mean the chopped-up condiment Americans usually call "relish." That's more akin to the feeling of being in a pickle than the feeling a nice, crisp gherkin brings to mind. The Merriam-Webster Unabridged Dictionary adds some weight to this theory by noting that in the U.K., being in a pickle means something more like "in a mess" rather than "in trouble," which is the more American sense.