Heavy sleeper.

The phrase 'heavy sleeper' is a straightforward descriptive term that combines the adjective 'heavy' with the noun 'sleeper.' To understand its origin, we can look at the individual components. The word 'heavy' has Old English roots, tracing back to 'hefig,' meaning 'having great weight, burdensome, difficult to lift or move.' Over time, 'heavy' developed a range of figurative meanings beyond physical weight. By the Middle English period, it was used to describe things that were dense, abundant, severe, or intense. For example, one could speak of 'heavy rain' or 'heavy labor.' The application of 'heavy' to sleep began to emerge to describe a profound or deep state of slumber, implying a resistance to external disturbances. The noun 'sleeper' also originates from Old English, 'slǣpere,' meaning 'one who sleeps.' It's derived from the verb 'sleep,' which itself comes from the Proto-Germanic '*slēpaną.' The combination 'heavy sleeper' likely became conventional as a natural and intuitive way to describe someone whose sleep is deep and not easily interrupted, contrasting with a 'light sleeper.' While it's difficult to pinpoint an exact first recorded use of the full phrase, its constituent words and their figurative applications have been present in the English language for centuries, making the compound term a natural evolution in describing sleep patterns. The concept of varying depths of sleep and the ease with which one can be awakened is a universal human experience, and English, like many languages, developed terms to articulate these differences. The simplicity and clarity of 'heavy sleeper' made it a widely adopted and understood idiom.