Nutmeg is the seed of a tropical tree that has been an important part of culinary and world history for hundreds of years. (The spice, mace, by the way, is from the same tree. It's the dried covering of the nutmeg seed.)
You may know the story of how Manhattan Island was traded to the English for nutmeg--in a way. From an NPR article:
In the 1600s, "the Dutch and the British were kind of shadowing each other all over the globe," explains Cornell historian Eric Tagliacozzo. They were competing for territory and control of the spice trade. In 1667, after years of battling, they sat down to hash out a treaty.
"Both had something that the other wanted," explains [culinary historian Michael] Krondl. The British wanted to hold onto Manhattan, which they'd managed to gain control of a few years earlier. And the Dutch wanted the last nutmeg-producing island that the British controlled, as well as territory in South America that produced sugar.
While you wouldn't trade an island for nutmeg these days, it's still a fairly expensive spice. I recommend not using pre-ground nutmeg. It loses it's pungency and flavor very quickly. Buy whole nutmegs and grate them as needed. It's strong stuff, so don't overdo it. But you'll reap the benefits--both flavor-and health-wise.
Like most spices, there are a number of health benefits to having nutmeg be a part of your diet. It is known to help reduce fatigue and stress. It's a sedative and pain reliever (an important part of Chinese medicine). Many use nutmeg to help digestion problems and it has antibacterial properties that can help eliminate bad breath. It's known to help with liver and kidney health, skin care and as a sleep aid.
So when you sprinkle a little bit of nutmeg on your egg nog this holiday, think about how you are continuing the great history of this little seed.