"Fiend-like queen"

In Act 5, Scene 8, Malcolm refers to Lady Macbeth as a "fiend-like queen" which I find interesting because Macbeth's real name is Mac Bethad Mac Findlach. Macbeth's last name looks a lot like "Fiend-like". Coincidence? I think Shakespeare came across this name in his Scottish research and used it in Malcolm's final speech on purpose. Lady Macbeth's real name btw was Grouch... ugh, what a beautiful name. If Shakespeare wanted to bestow a harsh name to a harsh character, he couldn't do much worse than Grouch.