Where does the milk in a coconut come from?

There's an issue here because coconut milk is actually slightly different to coconut water. It's coconut water that you find inside a coconut. That's not water that's got in from the outside, it's created by the coconut itself. It's actually what we call the endosperm of the coconut plant. That's the stuff that gives the nutrition for the developing seed, a bit like the flesh of a banana. As the fruit ripens, the coconut water gets converted into the solid fruit that you find in there. If you have an unripe coconut, the water will be quite sweet and very nice. The riper it gets the less pleasant it gets to drink.