The euphemism treadmill: you tell everyone to say “gay” not “homo” because “gay” means “light-hearted fun”, but then you find out that kids at school call each other “gay” in a mean way—so you start to consider if you can make “queer” mean “light-hearted fun”, even though previously you told everyone to stop calling people “queer”.
When there’s a euphemism treadmill, something is being covered up.
Today, we talk about “migrants” but before we spoke about “asylum seekers” and “illegal immigrants”.
As you can see from the graphs “asylum seekers” were a 1990s thing—a euphemism for the wars in the Balkans (“Albanian asylum seekers”).
This replaced “refugees”, a term that had by 1993 grown a bit shabby and dirty—a bit “1980s” and “LiveAid”.
So “asylum seeker” created sympathy, whereas “immigrant” was more neutral (incidentally, we speak about ourselves as “a nation of immigrants”, even Britain, because America is the hegemonic power and post-1860 she really did become a nation of immigrants, not colonists, and so to call ourselves “a nation of immigrants” is just Americanisation).
“Asylum seeker” also conjures up the image of active and empowered people, not dreary refugees trudging (refugees always trudge) to their new homes. Since they seek asylum it also creates the idea that there is immediate danger, not some passive threat they flee from.
In the 2010s, we moved from the tainted “immigrant”, now become pejorative, like “gay” in a playground, to the neutral “migrant”—the idea is that nobody “-ims” into or “-ems” out of anywhere, since “we’re all migrants really”, nobody belongs anywhere and the African in the Channel is much the same as the English computer programmer in Tokyo.
You can’t say there are good or bad migrants, or even productive and unproductive migrants—there are just migrants.
The most neglected term is “alien”—as in “illegal aliens”.
Indeed, the first conscious legalisation in Britain as regards immigration was called the Aliens Act.
It is hard to change linguistic trends, but I think “illegal alien” is a perfect phrase.