It turns out that the word "canvas" derives ultimately from the Latin word "cannabis"; which, of course, means "hemp."

Not only that, but apparently the word "hemp" itself may be distantly related to the Greek "kannabis," which was the source of the Latin "cannabis."

(All this according to MW3; I first encountered the connection between "canvas" and "cannabis" in a New York Times article on attempts to legalize industrial hemp production.)