Depending on which side of the border you hail from, the colloquial use of pickle can mean two very different things.
To be in a pickle is widely understood to mean one is in a spot of bother. On the other hand, a Scot may understand the word as pertaining to a small amount of something.
For example, if you wanted a pickle sugar in your tea, or a pickle salt on your chips, you would be asking for a wee bit on your beverage/takeaway. Note that you don’t need to say “a pickle of”.
The word has its origins in the 17th century, referring at first to grain. The grain at the top of a barley stalk was once referred to as a tap-pickle or end-pickle; contemporary usage grew from this derivation.
An alternate version is puckle, which is used just as often: this Scotsman headline illustrates a recent usage of the term, though it does break with the aforementioned convention of not using ‘of’: A puckle of words in the braw Scots tongue