This word has been a part of my brain since Bloom County came out years ago. A quick internet search shows that the fantastic, wonderfully funny and influential comic strip started in 1980. WOW I AM OLD! But I digress, no one cares how old I am, least of all me. Milo and Opus (seriously, if you have not read any Bloom County, go find some) work in the newspaper originally called the Bloom Beacon but subsequently changed to the Bloom:
Picayune -- Something that is trivial or of little value.
Now that could be a tongue in cheek, haha, clever joke and that would be the end of it. But no, there is much more to the story. There is a real newspaper called Times-Picayune and was immortalized in the song New Orleans Wins The War by Randy Newman:
This little cookie here's a macaroon
That big round thing's a red balloon
And the paper down here's called the Picayune
And here's a New Orleans tune
And the origin of this word?
There's some crossing over and mixed info on that, but basically a picayune was a Spanish coin, worth half a real. Its name derives from the French picaillon, which is itself from the Provençal picaioun, the name of an unrelated small copper coin from Savoy.
Aside from being used in Spanish territories, the picayune and other Spanish currency was used throughout the colonial United States. Spanish dollars were made legal tender in the U.S. by an act on February 9, 1793. They remained so until demonetization on February 21, 1857. The coin's name first appeared in Florida and Louisiana, where its value was worth approximately six-and-one-fourth cents, and whose name was sometimes used in place of the U.S. nickel. (source: wikipedia)
So you can see how the term went from a coin that was demonetized into basically being worthless could be "coined" (sorry...) trivial or worthless.