Okay a native speaker easily understands this as meaning in trouble, a sticky situation, a mess, a disagreeable situation, often embarrassing difficult, or disorderly. All in all in a pickle is a bad place to be. But how did it come to mean such a thing?
Turns out, as is not uncommon in the quirks of the English language that our good friend William Shakespeare had a hand in this “turn of phrase”(I’ll do that one another day). Although he is not the first to use this phrase he does immortalized it in his work “The Tempest” In a discussion between Alonso and Trinculo. Yay Shakespeare!
The reference however can be drawn back to the actual making of pickle (as a side/sauce not the dill your thinking of) all sorts of vegetables mixed together and pickled as a savory treat. This mixed up mess is a literal representation of the mess that a person may have found themselves in. I like this explanation best. It suggests a direct link/evolution from the idiom “in a stew” which is synonymous with “in a pickle.”
Although pekel the root word of pickle does not refer to the pickle sauce but the brine itself that preserves the vegetables, or meats. Historically ther have been people literally pickled. Which is icky and intriguing. Thomas Beaufort is a prime example and more famous would be Admiral Horatio Nelson. He was pickled in brandy and is probably the origin of calling a drunk person “pickled.”
There is a more gory reference I found coming from before Shakespeare (although he immortalized and improvised the language we must admit he was still following other authors) “The Morte Arthure” has a passenger that speaks of King Arthur’s diet and eating seven children with pickle. Thus the reference might point to this rather unfortunate situation! After all those children we most definitely in a mess, and quite literally in a pickle!
Before King Arthurs dinner, Shakespeare’s pilfering, and bodies being preserved the phrase seems to have been Dutch. The original idiom translates to sit in the pickle ( as in it’s brine). Which would sting, be sticky, and stink! But I do not speak nor did I research this phrase beyond it being the most likely origin of our well loved idiom “in a pickle” still it does seem like it would be quite a mess and were we to go and do this “we’d be in a bit of a pickle.”