Throughout the 19th century, news reports and medical journal articles almost always use the plant’s formal name, cannabis. Numerous accounts say that “marijuana” came into popular usage in the U.S. in the early 20th century because anti-cannabis factions wanted to underscore the drug’s “Mexican-ness.” It was meant to play off of anti-immigrant sentiments.
It was also used as a racist commercial to scare people off… Something along the line:
Hide yo kids, hide yo wife, they on marijuana rapin’ everybody out here