Opposite of disappointed

According to Oxford dictionaries, the derivation of disappoint is -

late Middle English (in the sense ‘deprive of a position’).

So I suppose the meaning of disappointment has extended over the centuries from the feelings of someone who didn't get a job they had wanted, to cover all kinds of disappointment. People sometimes amuse themselves by thinking of all the English words that exist in the negative form but no longer in the positive, like unkempt, uncouth and disgruntled.

Oh, and disgust comes from the French dégôut (distaste).