First - what does it mean? Well, if you're acting 'like a dog in a manger," you're selfishly withholding something that's useless to you from someone who could use it.
But where did the saying come from?
|Photo courtesy Steve Evans, via Creative Commons|
The Merriam-Webster Dictionary tells us that its origins are from an old Greek fable about a dog laying in a manger, not because he wanted to eat the hay but because he wanted to prevent an ox from being able to do so.
The first known use was in the second century CE by a writer named Lucian. It was first included in Aesop's Fables in 1476.
Sources: Merriam-Webster Online Dictionary and Wikipedia
Also: "The Works of Lucian of Samosata". Ebooks.adelaide.edu.au. 2009-05-01. Retrieved 2010-08-28.