Definition & Meaning of "like the cat that ate the canary"

What is the origin of the idiom "like the cat that ate the canary" and when to use it?

The phrase "like the cat that ate the canary" has its origin in English literature and dates back to the 19th century. The exact origin of the phrase is unclear, but it has been commonly used in various forms of writing, including novels, plays, and short stories.