Theory:

     The King and Queen of Siam had many daughters, and the Queen said that it confused her to have to remember so many names. One day the King decided to call them January, February, March (though of course in Siamese) till he came to the youngest whom he called September.
 
     The King of Siam had a peculiar habit. Instead of receiving gifts on his birthday he gave them. One year on his birthday, not having anything else handy, he gave each of his daughters a green parrot in a golden cage. The princesses were very proud of their parrots and they spent an hour every day in teaching them to talk. Presently all the parrots could say ‘God save the king’ and some of them could say ‘Pretty Polly’ in no less than seven Oriental languages.
Explanation:
 
"Princess September" takes place in Siam (Presently Thailand). We are informed that the King and the Queen have given birth to nine daughters. As a result, naming the princesses has become a tedious job. In addition, the queen frequently becomes troubled when recalling the names of her daughters. After reading the issue, the king mulls over a remedy to the imposed difficulty.
 
To make things simpler, the king decided to name his daughters in a specific order. He settled on the months of the year. As a result, he named his eldest daughter January and went on to name his youngest daughter September.
 
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The king, Queen and Princess
 
Commonly, monarchs' birthdays are celebrated as kingdom festivals. Thailand still observes a national holiday on July \(28\)\(^{th}\) (as of \(2021\)) to commemorate the birthday of their beloved King Vajiralongkorn.
 
The King from "Princess September" had an unusual birthday celebration, defying the conventional birthday ceremony. He preferred to distribute gifts to receiving a few for himself.
 
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The act of gifting each other
 
Unfortunately, the King had no useful presents for that recent birthday. The king later gave each princess a green parrot in a golden cage.
 
This unique present enthralled the princesses to no end. The princesses were quite proud of their parrots. They spent an hour each day teaching them how to communicate. As a result, all of the parrots became fluent in uttering "God save the King" and "Pretty Polly" in seven distinct Oriental languages.
 
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A parrot in a golden cage
 
"God save the King" is a popular royal hymn of the world's realms. It demonstrates the people of the kingdom's allegiance to the ruler. Likewise, "Pretty Polly" is a common folksong found in the North American and the British regions of the world. Commonly, "Pretty Polly" is one of the first few phrases taught to parrots.
 
The term Oriental is used in British English. It is used to indicate the Eastern and South-eastern countries. As mentioned in "Princess September", the narrative is set in Thailand, an Oriental country.
 
Meanings of difficult words from the paragraphs:
 
S.No
Words
Meanings
1
SiamPut forward a plan or suggestion for consideration by others
2
PeculiarBeing the only existing one of its type or, more generally, unusual, unique or special in some way
3
HandyUseful or convenient
4
OrientalThe countries of East and Southeast Asia
Reference:
National Council of Educational Research and Training (2008). It so happened. Princess September - Somerset Maugham (pp. 34 - 44). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.