manners (n.) Look up manners at
"external behavior (especially polite behavior) in social intercourse," late 14c., plural of manner.
Under bad manners, as under graver faults, lies very commonly an overestimate of our special individuality, as distinguished from our generic humanity. [Oliver W. Holmes, "The Professor at the Breakfast Table," 1858]
Earlier it meant "moral character" (early 13c.).