However, it turns out it’s real definition means hunter and is derived from the biblical figure, who was a great hunter and descendant of Noah: Nimrod.
Wondering how a great hunter would become the slang for idiot, I decided to dig a bit deeper.
According to The American Heritage Dictionary, nimrod being a slang for idiot probably started during a conversation between Bugs Bunny and Elmer Fudd in an episode of Looney Toons:
ETYMOLOGY: […] probably from the phrase “poor little Nimrod,” used by the cartoon character Bugs Bunny to mock the hapless hunter Elmer Fudd.
As someone on Urban Dictionary puts it:
Warner Brothers’ Looney Toons cartoons were not written for children, but for literate adults, and often contained literary references children would not understand. Younger generations, mostly illiterate, and having little or no Bible knowledge not gleaned from their moronic parents and half-wit talk radio hosts, probably misunderstood the comment as being a general insult describing the slow-witted Fudd.
So there you have it. When Looney Tunes was trying to say “poor little hunter”, viewers not knowing what “nimrod” really meant, tried to use context and derive the meaning of nimrod, and came out with “poor little idiot”, leading up today’s slang.