What Makes Mysteries So Cozy?

They call them cozy mysteries. But what's cozy about murder and mayhem? Why is it cozy when the wrong person gets accused of a crime? Or when a group of geriatric gumshoes put their lives on the line?

Of course, it's not the murder and mayhem that make the novel cozy, nor the witches and sweet old ladies (or old gents). Perhaps it's that contract between author and reader--the one where we know it's all going to work out right, somehow, in the end; and the knowledge that all of the suspects ar...