Someone watching a small child get drowsier and drowsier might comment with a chuckle that they will soon be in the land of Nod, meaning that they’ll soon be asleep.
Nod was a biblical region, or country, mentioned in the Book of Genesis. Separately, the English verb nod — especially in the phrase nod off — refers to the head dropping while falling asleep. One might say, "I nodded off during the long lecture" or "The warm air had me nodding at my desk." In a clever 18th-century pun popularized by author Jonathan Swift, the land of Nod became a playful way to describe the state of sleep as the "sleep country."