IMO it stretches credulity to imagine that Card, who seems to have been writing novels for a decade before 'Ender's game', would not have a grasp of the meaning of words. Afterall, if I was writing a Sci-Fi saga I'd agonise for weeks over what to call the antagonists.
The fact that in the last decade he has apparently ret-conned the "Buggers" to have a different name "Formics" which he used becasue it is derived from the Latin for Ants, suggests he has a deep understanding of the meaning and entymology of words.