A chap in the pub today told me that something was "picayune", and I had no idea what he meant. It panicked me. It embarrassed me. I felt like a picolexical dolt. Just so this never happens to you: if something is picayune it means that it's so small that it's not worth considering. The name derives from an old Spanish coin that was worth half a real. So it's the equivalent of the English phrase tupenny-hapenny.
As Spanish money used to be legal tender in the USA, I can tell you that a picayune was equivalent to six and a quarter cents. Apparently the word picayune used to be quite common in England; but then again, so did smallpox.
The Horologicon is a book of the strangest and most beautiful words in the English language arranged by the hour of the day when you will really need them. Words for breakfast, for commuting, for working, for dining, for drinking and for getting lost on the way home. It runs from uhtceare (sadness before dawn) to curtain lecture (a telling off given by your spouse in bed). It's out on November the first, but you can already order it from these lovely people: