The dihydrogen monoxide hoax involves calling water by the unfamiliar chemical name “dihydrogen monoxide” (DHMO), and listing some of water’s effects in an alarming manner, such as the fact that it accelerates corrosion and can cause severe burns. The hoax often calls for dihydrogen monoxide to be regulated, labeled as hazardous, or banned. It illustrates how the lack of scientific literacy and an exaggerated analysis can lead to misplaced fears.
The hoax gained renewed popularity in the late 1990s when a 14-year-old student collected anti-DHMO petitions for a science project about gullibility. The story has since been used in science education to encourage critical thinking and avoid the appeal to nature. (Source)