In this phrase, 'Nod' does not refer to an actual place, but to a state of sleep or rest. He nodded off in the meeting and was in the land of Nod in no time.
Pro Tip 2/3
Not Literal
Don't misunderstand it as someone actually going to a place called Nod; it's about falling asleep. After a long day at work, she quickly went to the land of Nod.
Pro Tip 3/3
Poetic Use
Often used in a poetic or quaint way to express the idea of someone sleeping. The baby's in the land of Nod after the lullaby.