From Daily Writing Tips:
I’ve been bingeing on the Shetland mysteries by Ann Cleeves and have finished them all. The novels are set in the Shetland islands to the extreme north of the UK. One of the many enjoyable features is the realistic dialogue, replete with dialect words and British idioms. I encountered several words, some of them insults, that sent me to the dictionary.
In researching insults in general, I came to realize that English provides an astounding number of ways to show contempt for our fellow creatures—too many for a single post.
I shall begin with thirty words used to insult the intelligence.
Compounds involving the head
One way is to form a compound with head, brain, skull, or wit:
NOTE: The definition of wit referenced in these compounds is “The faculty of thinking and reasoning in general.”
Words for mental conditions
Some words used to call a person stupid or foolish were or, in some contexts still are, medical or legal terms. The Ngram viewer shows all of these especially offensive insults understandably declining—until the 2000s, when they began climbing. The word idiot shows an especially dramatic spurt as we enter the age of incivility at the highest levels.
idiot: A person so profoundly disabled in mental function or intellect as to be incapable of ordinary acts of reasoning or rational conduct; specifically a person permanently so affected, as distinguished from one with a temporary severe mental illness.
imbecile: (Latin imbecillus “weak, feeble, delicate, fragile, ineffective, lacking intellectual or moral strength”) Of a person: mentally weak or deficient; lacking in intelligence or intellectual ability; stupid, foolish, idiotic. Sometimes used with the medical meaning of “suffering from mental retardation, typically of a moderate or severe degree,” but now largely disused and often considered offensive.
Link to the rest at Daily Writing Tips
If you’re not familiar with the Ngram Viewer, it’s a Google Books project you can find here.