where did the word 'Marijuana' come from?

The word `marijuana' is a Mexican slang term which became popular in the late 1930's in America, during a series of media and government programs which we now refer to as the `Reefer Madness Movement.' It refers specifically to the medicine part of cannabis, which Mexican soldiers used to smoke.
Today in the U.S., hemp (meaning the roots, stalk, and stems of the cannabis plant) is legal to possess. No one can arrest you for wearing a hemp shirt, or using hemp paper. Marijuana (The flowers, buds, or leaves of the cannabis plant) is not legal to possess, and there are stiff fines and possible jail terms for having any marijuana in your possession. The seeds are legal to possess and eat, but only if they are sterilized (will not grow to maturity.)
Since it is not possible to grow the hemp plant without being in possession of marijuana, the United States does not produce any industrial hemp products, and must import them or, more often, substitute others. (There is a way to grow hemp legally, but it involves filing an application with the Drug Enforcement Administration and the DEA very rarely ever gives its permission.) This does not seem to have stopped people from producing and using marijuana, though. In many of the United States, marijuana is the number one cash crop, mostly because it fetches a very high price on the black market.