The History of Rakhi is little known but there are said to be a lot of incidents that give a perspective to the history of this festival.
King Bali and Goddess Laxmi
One can say that the History of Rakhi begins with the incident that is mentioned in a Hindu scripture where it says that during an incident Indira; the Lord of sky, rains and thunderbolts, was disgraced by the demon king Bali because of which his wife Sachi spoke to Vishnu who gave her a cotton thread bracelet which she was to tie on the wrist of her husband. She did as she was told and prayed for his well-being and victory. With this began the inspiration of the protective thread. Though in this incident the highlight was simply the holy thread that women used as their prayers for their men going to war and this thread nowhere was limited to a brother sister like relationship. But it was here where the power of the holy thread began to gain significance.
But first reference to the history of Rakhi where it is a bond between a brother and sister goes back to the legend where Lord Vishnu won the worlds from demon King Bali after which, on the request of Bali, Lord Vishnu moved into his palace. However, Goddess Lakshmi did not approve of the palace and the growing friendship between Bali and Lord Vishnu. Affected by this, she went to Bali and tied a Rakhi to make him her brother and in return asked him to free Lord Vishnu from the request to live in his palace. This request was accepted by Bali and with this he accepted Goddess Laxmi as his sister.
Lord Krishna and Draupadi
The most common incident that relates to Rakhi whenever there is any mention about the history of Rakhi is the one between Lord Krishna and Draupadi. The relation between them goes back to the point in Mahabharata where Lord Krishna gets injured during a battle where Draupadi ties a strip of cloth around his wrist to stop the bleeding. Touched by this incident, Lord Krishna promises that he would protect her from all evil and danger. And standing true to his promise, Lord Krishna protects Draupadi during the Cheerharn incident that takes place when Pandavas lose their wife in the game of dice to Kauravas.
The story of Yamuna and Yama
Another historic event that relates to the History of Rakhi is the tale where Yamuna asked Lord Yama who is the Lord of Death, to visit her. When Lord Yama visits Yamuna she ties a Rakhi to him and asks for immortality. This gesture moved Lord Yama and he declared that whoever gets Rakhi tied by his sister and promises her to stand by her and protect her,whatever come may will become immortal.
Incident between Rani Karawati and Emperor Humayun
It was during the medieval era where Rajputs were battling against Muslims to avert their invasion that Rani Karawati who was the widowed queen of King of Chittor sent a Rakhi to emperor Humayun as she realized that she would not be able to defend the invasion of Bahadur Shah, who was the Sultan of Gujarat. Touched by this gesture, Emperor Humayun came to her rescue and with the help of his troops protected her. This became an important incident in the history of Rakhi citing the strength of this thread once again.
Apart from this there have been other examples that go back to 300 BC where Alexander's wife Roxana asked King Poras to accept her as his sister and because of this he avoided attacking Alexander the Great during war. These examples all together state the power of this relationship. None of them were brothers and sisters by blood but nevertheless, standing true to their promise each proved the sacristyof this relationship. Though there is no one incident that talks about the history of Rakhi and cite how it all began but all these incidents togetherdid establish the power of this thread and the bond between a brother and sister; whether in the relation by blood or brought together by destiny! And today it is this bond that is celebrated all across the world with same spirit and enthusiasm.