A fable from Aesop

A 'manger' holds  food for cows to eat. One day a dog saw a manger and decided to sleep in it. When the cows which used to eat from the manger came near, the dog growled and barked at them. So even though the dog could not eat  straw, he stopped others from eating it.

So today a person who stops others from using things he can't use himself is called 'A dog in the manger.'