The Oxford English Dictionary has set up rather a good site to try to trace the first usage of various well-known science fiction terms. Sci-fi fans are invited to contribute: given the number of knowledgeable people about here, follow the link and it's not inconceivable that you could be a contributor to our national language!
Can you better an 1828 first siting of "alien" to mean extraterrestrial? Or "teleport" (1944), or "warp speed" (1977)? Click and try!
Link: Jesse's word