Omnium wrote:
"Didn't he write originally in German, and wouldn't the use of the word "illusion" have been chosen by a translator, not by Freud?"

I'd have to go and check on whether Freud only wrote in German, but I'm fairly certain that he also spoke english, and there's also the fact that in his writings he distinguished "illusion" from "delusion".

Also, aside from this issue, I'm also wondering if perhaps someone knows the etymology of these two words and what roots separate one from the other etymologically. I am by no means a linguist, but I'm guessing there's probably some latin root word like "lucere" which means to illuminate, and these two somehow are born from there. But I'd much prefer to leave that sort of work to the real experts who haunt the shadows of this electronic nether world.