Let's start with the truth. Water does not flow up a hill. So why would Jack and Jill go up the hill to fetch a pale of water? You know it does not rhyme if they went down the hill.
Any Congolese girls would probably shake their heads or roll their eyes at such silliness. They know that they have to go down the hill to fetch water. They have carried too many full buckets and jugs up the hill.
The way home is up the hill. Also, they know that five gallons of water weighs over 40 pounds, too.
