My old friend Richard Brockhaus long ago asked this question. Thank heaven he didn’t ask me his favorite question, the one he submitted to Saturday Night Live where it was read on a show: “What was Captain Hook’s name before he lost his hand?” That would have placed me in a pickle.
“We’re in a real pickle now” Sam says to Frodo. In my youth, being in a (baseball) rundown was called “being caught in a pickle”. Where does this come from?
In Fayetteville, NC, in the 1950’s to be or get into a pickle simple meant to be or get into a problematic situation. The girls used it more than boys, as I recall. The reason I seldom used it is that I was an interloper from red-neck country, where “step in s–t” was the preferred expression for the same meaning.
All of this, of course, is beside the point. According to most etymologists, the origin of the phrase “to be in a (pretty) pickle” is the Dutch language, where “in de pekel zitten,” “iemand in de pekel laten zitten” has been around for at least 400 years. The word pekel in Dutch can refer to the pickle or the brine that makes pickles. So the lost image is someone sitting in the brine waiting to become a pickle, probably a frightening thing when pickles were first being produced. This usage goes back to 1573, maybe 1562.
An interesting sidelight not unrelated to the meaning of the phrase: In the same century our British forebears used the phrase “in pickle” inside another phrase: “a rod in pickle”. This harkens back to the time when beating children with a rod no thicker than the thumb just didn’t do the job, so the rod used was left standing in salt brine to move the pain up a notch or two.