Re: "Why is any object we don't understand always called a thing?"
Using the word thing
could suggest a belief that the referred-to object might cause problems. I always thought that that prejudice was what McCoy was objecting to.
Also, cf The Thing from Another World.
“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)