Nincompoops all around

Sometimes I learn interesting new stuff. Even when I don't mean to.
I was blustering about someone--I don't remember exactly who, but I'm betting it was a politician--when I uttered these words:
"That guy is a total nincompoop."
My grandsons, who were busy planning the destruction of a lego city on the floor near my feet, froze.
Nincompoop?
I saw a look pass between them. It's one I've seen before, ever since I started having kids of my own.
"What's the old fool talking about now?"
Then they shared a quick, slightly scandalized laugh.
I realized they were reacting to what they perceived as a daring scatological meaning for the otherwise indecipherable term.  After all, the word I had just uttered ended in "poop," and we all know what that is.
Finally, grandson Cyrus, who is the older and bolder of the two, put the burning question into words:
"Grandpa, what's a nikopoop?"
Despite the mispronunciation, I knew what he was asking, so I hastened to reply.
One thing, though.
I couldn't.
Oh, sure, we all know that it's an unflattering term meant to describe someone without much sense or intelligence. But why? Since when?
The origin of some common insults, like airhead, numbskull and blockhead, are pretty obvious, but there's a whole host of popular pejoratives with backgrounds that defy easy understanding. I thought it would be kind of fun to find the answers, counting on a few internet searches to reveal what etymologists--the pointy-headed guys and gals who track down the history of words--had to say about my grandsons' favorite new descriptive term. Well, I discovered that it wasn't quite as interesting as I hoped it would be. Various theories include root words from both Latin and Dutch, plus a slightly more intriguing idea that links Nincompoop with the given name Nicodemus, who naively questioned Christ in the Gospel of St John. In fact, this word still exists in French as nicodème, meaning a simpleton.
But it was in the thesaurus section--the area where words with the same meaning are listed--that I discovered the real treasure trove.  Suddenly, I felt my personal vocabulary of rude and useful words expanding. No longer would I have to settle for anything commonplace when referring to, say, congressmen, umpires or members of the Green Bay Packers.
Words like  dizzard, ninnyhammer and hoddy-doddy will now flow smoothly off my tongue. Imagine the impact the first time I call someone a doodle or a dunderpate. Or when I mention that someone is a real gowk, gawk or jobbernowl? Or even a dotard, a driveler, or my personal favorite, a henhussy?
My mind reels with the possibilities.
Of course, I'm not going to share any of this stuff with my grandsons. I know I confuse them enough already. Plus, I'm almost certain they already think I'm kind of a, well, you know.
A nincompoop.