Since we're talking about it, can anyone confirm what "Marijuana" originally meant?

I saw on some video that marijuana meant "cheap tobacco" in Spanish. (is that so?)

Since Cannabis is the name of the genus, I think (if one comes to be) we should call it Cannabis subforum.

Then I have the question: what Cannabis means?

I read that "Canna" meant dog, and "bis" meant two, so from that source, Cannabis means "two dog plant".

Anyone want to comment on this?