The term Martian refers to anyone or anything originating on the planetMars.
In the early 20th century, when many believed that Mars was inhabited, the term was applied to "little green men" originating there. The term even became synonymous with "extra-terrestrial", as any "aliens" were assumed to be of Martian descent.
In a deleted scene from ENT: "Storm Front", the Martians in The War of the Worlds were referred to as having inspired mass panic in the United States of America by people who feared real Martians were coming to invade Earth. In the same deleted footage, Sal admitted he sometimes wished the Martians had come.
When Amelia Earhart was confronted with an Ocampa accompanying several Humans who encountered her in 2371, she assumed that the Humans were trying to trick her into believing Martians had invaded Earth. (VOY: "The 37's")