Theory:

"Taro's Reward" is adapted from the Japanese fairy tale called "The Enchanted Waterfall". The date of the origin of the story is unclear as the story is very old. But in the year \(1892\), the story was retold in English by Mrs. Kate James and was published in a book called "Japanese Fairy Tale Series" by a Japanese publisher called Hasegawa Takejirō.
Legend says that the story is based on true events. In somewhere around the \(8\)th century, there lived a poor woodcutter. His father was very sick, and he had always worked hard to support him. One day he went to the forest to find some firewood to keep his father warm. There he came across a waterfall.
 
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The woodcutter discovers a waterfall in the middle of a forest.
 
All of a sudden, the water from the waterfall turned into saké. He took some of the saké to his father. The father drank the saké and became healthy. The story then reached the Empress Gensho.
 
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The Empress of Japan
 
Soon she came and drank from the waterfall. She was so amused that she renamed the period she ruled as Yoro.
What is more fascinating is that the waterfall around which the story revolves is real and could still be seen in Japan. It is called Yoro Falls and is located in the Yoro District of Gifu, Japan. Although the water from the falls do not taste like saké, it is quite famous for its quality and purity.
 
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Yoro Falls
  
If you are interested, you can listen to the original fairy tale here. While at it, try looking at the similarities and the differences between "Taro's Reward" and "The Enchanted Waterfalls".
 
Reference:
*The enchanted waterfall: ttps://www.nlb.gov.sg/biblio/9850859.
 
Video Courtesy: #1 Marmaduke fan.< https://www.youtube.com/watch?v=OnY8DhEAeGs&ab_channel=%231MarmadukeFan >