What is the origin of the idiom "famous last words" and when to use it?

The idiom "famous last words" originated from the idea that someone's final statement before a significant event or outcome is often ironic, misguided, or ultimately proven wrong. It implies that the person's confident or bold assertion will be proven wrong or contradicted by subsequent events. The phrase is often used humorously or sarcastically to highlight the unpredictability or irony of a situation. It underscores the notion that making bold predictions or assumptions can be risky or ill-advised.