Is a boor somebody who boos or somebody who bores?
Boors can be boring, at best. More likely, boors are just rude (think cell phone conversations in the movies or nose-blowing at the table when somebody's eating — boo!).
Great authors wrote references to boorish behavior into their literary works, such as Henry Adams in the Education of Henry Adams:
Adams could not get over his astonishment, though he had preached the Norse doctrine all his life against the stupid and beer-swilling Saxon boors whom Freeman loved, and who, to the despair of science, produced Shakespeare.
And in Charles Dickens's Great Expectations:
"Pip," said Estella, casting her glance over the room, "don't be foolish about its effect on you. It may have its effect on others, and may be meant to have. It's not worth discussing."
"Yes it is," said I, "because I cannot bear that people should say, 'she throws away her graces and attractions on a mere boor, the lowest in the crowd.' "
As written by William Makepeace Thackeray in Vanity Fair:
. . . for boor as he was, Sir Pitt was a stickler for his dignity while at home, and seldom drove out but with four horses, and though he dined off boiled mutton, had always three footmen to serve it.