(covers information from several alternate timelines)
In the early 20th century, when many believed that Mars was inhabited, the term was used to "little green men" originating there. The term even became with "extra-terrestrial", as any aliens were assumed to be of Martian decent.
The War of the Worlds featured Martian invaders, who's appearance was said to have a strange horror. (ENT: "Similitude"). Incredible Tales of Scientific Wonder also featured stories about "men from Mars". (DS9: "Far Beyond the Stars")
When Amelia Earhart was confronted with an Ocampa accompanying the Humans who encountered her in 2371, she assumed that the Humans were trying to trick her into believing that Martians had invaded the Earth. (VOY: "The 37's")