We'll look at it this way: that's why characters in books always "grunt". Like "I answered. The old man just grunted" because he is content with what you answered.
All words are beautiful. You have no right to judge gruntled for being the way it is. Just because disgruntled has makeup doesn't make it more beautiful. At least gruntled has the confidence to be naturally beautiful. Stop the hate.
Then Disgruntled = Displeased, dissatisfied and discontent