Our thanks to the always outstanding Everlasting Blรถrt for referring us to the Historical Dictionary of Science Fiction that gives the etymology of words and phrases in the genre and expounds on their earliest citations (see also for general use). 
Unobtanium, for instance, predates Avatar by a half a century, first in print as a bit of industry jargon that researchers working on the noses of intercontinental ballistic missiles sought after in 1956. Warping space-time as a means of travel dates back to 1936 J. Williamson’s short story Cometeers. Before Chewbacca, in Lucas’ dystopian directorial debut THX 1138 there was the line: “I think I ran over a wookiee back there on the expressway.”
