On April 21, 2016, U.S. Army Chief of Staff Gen. Mark Milley delivered a speech at a military reserve training program at Norwich University in Vermont. At the time, he likely didn't expect that his words would fuel widespread speculation on the internet about the military engaging with UFOs and extraterrestrials.
Then again, he did tell an audience of cadets, "You'll be dealing with little green men," the Army Times reported. [Greetings, Earthlings! 8 Ways Aliens Could Contact Us]
The general was probably using a more recent version of the phrase "little green men" that refers to military personnel in Russia and Ukraine — so-called because of the color of their uniforms, the BBC explained.
But for many people, "little green men" means just one thing: extraterrestrial life. This description of alien beings — which are usually mischievous or even downright malevolent — has endured as a staple of science-fiction vocabulary for many decades, appearing in countless sci-fi stories, movies and television programs.
But where did the idea of diminutive, verdant, otherworldly invaders come from, and how did it come to be so widely accepted as a way of referring to visitors from other worlds?
It's not easy being green
The trope may actually predate science fiction itself, hearkening back to a 12th-century English legend known as "The Green Children of Woolpit," said Arthur Evans, managing editor of the journal Science Fiction Studies (SFS) at DePauw University in Indiana.
In a 2006 study published in SFS, scientists described this folktale, which recounts the unexplained appearance of two children with green skin near the village of Woolpit in eastern England, Evans told Live Science in an email.
In science fiction, use of the phrase "little green men" dates back to the 1940s, with the Encyclopedia of Science Fiction tracing the first usage to the story "Mayaya's Little Green Men" (Weird Tales, 1946) by Harold Lawlor.
Frederic Brown's popular science-fiction novel, "Martians, Go Home" (E.P. Dutton, 1955) reinforced the idea of small, green-skinned alien invaders that are more irritating than dangerous. Rather than engaging Earth's armies in deadly battles for global domination, Brown's little green men preferred to spend their time playing annoying and embarrassing pranks. [7 Huge Misconceptions about Aliens]