The word marijuana has quite the muddled backstory, and was omnipresent throughout Latino linguistic culture. The word was first attested in its current usage under the form mariguan, in an 1894 edition of Scribner's Magazine. This seems to be where most other forms of the word stem from, mostly switching the centric g with an h: variations such as marihuma, mariahuana, mariahuano, marihuano, and marihuana could be seen to crop up in the next twenty years. In the late 1910s, several newspaper articles and bits of gossip unfairly attributed the drug only to Mexicans, and so people began to folk etymologize the word. Since weed was thought of as Latino primarily, people began to alter the word to marijuana from the most-common marihuana simply because the new form sounded more like a common Hispanic name, Maria Juana. Indeed, some people persist to today in calling it Mary Jane, another derivative of this false and somewhat bigotedly folk etymology. But where did mariguan come from? Etymologists theorize that it is of Native American origin (like the cultivation of the plant), and it may stem from the Nahuatl word for "prisoner", presumably because one under the influence of Mary Jane was a "prisoner" to the effects of the depressant. If this is true, marijuana is ultimately of Uto-Aztecan descent.
An excellent, contributing research article about this may be found here: www.sino-platonic.org/complete/spp153_marijuana.pdf
Adam Aleksic, a freshman studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in words, vexillology, geography, board games, limericks, and law.