Sheeple are people who mindlessly follow a trend or mass movement. Individuals who do not think on their own and do not form their own opinions, accepting as factual anything reported in mainstream media. The word is also used to refer to people who are conformists or submissive.
The word is a portmanteau (two individual words combined to form a new word) — composed of the words “sheep” and “people.” The word first appeared in print in an article in the Emory University Quarterly in 1950. The word has been connected to John Brunner’s science fiction novel, The Sheep Look Up, published in 1972, that predicts the destruction of the environment in America. In the novel, people are compared to sheep and the cover features an illustration on people looking at the heavens while wearing stylized gas masks with curved sheep’s horns in the back. The word reappeared in the Wall Street Journal in an article in 1984. Despite its appearance in print and its use on the web (particularly in the comment sections of political stories that are rife with mudslinging), the word is not included in the print edition of the OED (perhaps the word rubs the editors the wrong way), but found in several American dictionaries, such as the American Heritage Dictionary of the English Language (5th Edition).