I find this highly interesting. I love discovering the hidden origins of idioms like this. Like making money hand over fist.

Interesting sidenote. Before Bugs Bunny started calling Elmer Fudd a nimrod, the word nimrod had never meant idiot. The reason Bugs Bunny called him a nimrod was to lampoon and mock Elmer Fudd who was a poor excuse for a hunter. What Bugs was actually doing was comparing the inept Elmer to the biblical character Nimrod, a mighty hunter from the bible.

In the long span of human history before Bugs, Nimrod—a biblical figure—was a hunter. He was king of Shinar, son of Cush, and great-grandson of Noah. According to the Bible (Genesis 10:8–9, for the curious): “And Cush begat Nimrod, who began to be mighty in the earth. He was a mighty hunter before the Lord.”

Nimrod was as far from Elmer as you could get which was why Bugs called him that. While the comparison wasn't accurate, his tone was easy to recognize as contempt. That's why children who grew up watching Bugs Bunny understood the insult nimrod to mean idiot.

Also, Bugs had a famous line in one of the episodes with Wile E. Coyote. It was the first time Wile E. ever talked. He declares he's a genius, but after losing to Bugs over and over again, he shows up at Bugs rabbit hole, erects a door and knocks on it. When Bugs answers it, Wile E. who is black and burnt says "Allow me to introduce myself. My name is Mud."

This is a saying that means I am a disgraced. Wile E. had begun the episode by introducing himself to Bugs and declaring himself a genius. Throughout the episode, Wile E. exhibited a bloated and overblown sense of greatness, but by the end, he ended up defeated by Bugs. The origin of this saying "My name is Mudd" is in reference to Dr. Samuel Mudd who conspired with John Wilkes Booth to kidnap and/or assassinate President Lincoln. In the end, the respected doctor who many treated as a genius ended up sentenced to life in prison for his role. He was the one who treated John Wilkes Booth's leg after he broke it leaping from the theater balcony.

Because it's Bugs, Bugs Bunny turns this declaration of defeat in a humorous observation. Wile E. passes out after delivering the line prompting Bugs to break the fourth wall as he looks at the camera and reminds the viewers, "Remember, Mud spelled backwards is Dum."

Despite Dum being a homophone for the word dumb, it was also Bugs spoofing a laxative commercial slogan of the times called Serutan which when spelled backwards was Natures as in Natures Laxative. That's why Bugs wags his eyebrows after saying it. It was the show creators giving the audience a wink and nod asking us, You get it? Do get the joke?

I love reserching old idioms. They're fascinating.