I first heard/read the term “the chosen people” when I was in my 40’s.
I have a confession to make--
From my 14th birthday+/- until 25th+/- birthday I only knew the New Testament from a Catholic point of view and a Baptist’s point of view as seen through the verses in the New Testament. I do not recall hearing or reading the term “Old Testament” until I was past 40 & now, I’m over 70.
Not being Jewish & only reading the Old Testament I never knew how much involved the Lord was with the Israelite people, It wasn’t until I read The Old Testament that I learned how involved the Lord was with His Chosen, the Israelite people in The Old Testament.
There the Lord did single them out in the following verses.
(Deu 7:6 KJV)
For thou art a holy people unto the LORD thy God: the LORD thy God hath chosen thee to be a special people unto himself, above all people that are upon the face of the earth.
(Deu 7:7 KJV)
The LORD did not set his love upon you, nor choose you, because ye were more in number than any people; for ye were the fewest of all people:
From those verses and onward I learned that the Lord set out conditions that they must follow to get His eternal grace.
I did not understand what this all meant until I came across the site below that I found on the internet.
Love the Stranger as thyself
This helped me make since of this, does it help you too-?

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I would consider the Old Testament as mostly fiction. Especially Exodus. The Old Testament claims Moses fled with the Israelites from Egypt, as they were slaves.
Problem: Evidence exists that the workers were actually paid (believe it or not, they kept records, even back then).
Problem: The deaths of the Pharaohs are on record and not a one, drowned in the Red Sea, pursuing the Jews.
Problem: There could have not been an Eden, where everything was perfect. Many creatures were in existence that pre-date man; especially insects (blood-sucking mosquitos, biting flies, spiders, stinging bees, wasps, biting centipedes, biting ants, scorpions, fleas, mites, lice, chiggers, ticks, et cetera).
People in tribes would see their fellow tribesmen/women, die and decay. This scared them and they would go to their tribal shamans, for answers, he or she would concoct tales in an effort to alleviate their fears. As they were very superstitious, whatever the shaman told them would be believed.
As societies became more structured, these shamans would remain highly respected and once the shamans learned to write, they would write down their tales. Over time, whether one is in a society in Egypt, or any other society, their shamans (Clerics) would continue writing down not only their ideas on how things began, but also laid down laws for the people to follow, to maintain order.
Take everything in such books, whether it is the writings of Buddha's sayings, the tales of how things began handed down by Native Americans, or, the stuff of the Abrahamic religions. They all have their own ideas, but no one has all the answers and what has been written is, with the exception of some war conflicts that have been written into these texts, just a way of controlling society and trying to allay their fears of an actual end to life.