Thank you, that´s certainly interesting. Still it seems the usage has considerably increased since the late 70s early 80s. I also think they never claimed to invented or redefined the word, just highlighted a certain aspect that was used a lot less before that.
Today when you ask anyone on the street for their first assocication with the word alien they would probably think of extraterrestials and not immigrants. That might have been different in the 1950s.
But maybe someone whose first language is english would disagree, I don´t know.