The word Marijuana entered English usage in the late 19th century. According to the Oxford English Dictionary, the first known appearance of a form of the word in English is in Hubert Howe Bancroft’s 1873 The Native Races of the Pacific States of North America. Other early variants include “mariguan” (1894),[12] “marihuma” first recorded in 1905, “marihuano” in 1912, and “marahuana” in 1914.[19] According to the second edition of Webster’s New International Dictionary. the word originally denoted a species of wild tobacco.
The use of “marihuana” in American English increased dramatically in the 1930s, when it was preferred as an exotic-sounding alternative name during debates on the drug’s use. It has been suggested that in the United States the word was promoted by opponents of the drug, who wanted to stigmatize it with a “foreign-sounding name”. According to Lizzie Post, the word “marijuana” is deprecated because “in the early 1900s, the term marijuana was purposely used to negatively associate it with the Latino community.” The word was codified into law and became part of common American English with the passing of the Marihuana Tax Act of 1937.
The word Cannabis has much simpler roots… The plant name Cannabis is derived originally from a Scythian or Thracian word, which loaned into Persian as kanab, then into Greek as κάνναβις (kánnabis) and subsequently into Latin as cannabis.