The term is in reference to the last scene in the popular children's fairy tale Rumpelstiltskin, in which Rumpelstiltskin's name is guessed, causing him to become fairly enraged, and stomp angrily on the ground, like a child.
It is commonly used in terms with other words that rhyme with it, notably "Stumpy" and "Grumpy".
"You're such a grumpy Rumpy."
"What an attention whore that Rumpy is."
"I was watching the rumpy baseball game and the rumpy Cubs lost again."