If you're contented, you're happy and not complaining.
In the early 1900s, a dairy company cleverly used the word in their advertising slogan — "Milk from contented cows." Who wouldn't like to imagine cows without a care, contented and grazing in sunny, green pastures, every now and then emitting a satisfied moo? The company, which is still in business, became known by that slogan, which they used for many years. They even sponsored a radio show called "The Contented Hour," broadcast from 1931 until 1951.