There are three stories told of why the practice of Kurukulle came to be given by the Buddha. Avalokiteśvara tells of these three stories, and I will list them here below.
1️⃣
Once when young Rāhulabhadra had gone to Rājagṛha to receive alms, he went to the Veṇuvana grove, and there descended into a long pond to wash his alms-bowl. While there, he, the son of Yaśodharā, was mistaken for a white ascetic and so was pulled into the pond. At that time the young Rāhulabhadra recited this spell. No sooner had he recited the mantra than— just like someone emerging from his house—he arrived in the presence of the Blessed One.
Having approached the Lord, he said, “Father, I have seen the power of the secret mantra which you have granted.”
The Blessed One spoke: “Where have you seen that?”
“In the presence of the nāgas. Therefore, I request that the Blessed One teach this mantra, so that other beings too may be protected by it.”
So then, at that very time and on that occasion, the Lord dispatched Vajrapāṇi, and benevolently granted this mantra and this manual of instruction to the listeners and the bodhisattvas, to monks and nuns, and to male and female lay practitioners. Therefore, children of noble family, one who creates a sandalwood maṇḍala and reads this mantra and this manual of instructions will not be harmed by poison, will not die from poison, will have no fear of boils, eczema, leprosy, disease, nāgas, snakes, tigers and other beasts of prey, weapons, enemies, poverty, or untimely death. None of these will occur.
2️⃣
In order to protect the Teachings, the Lord granted Mahākāla the demoness Hārītī, whom he had nourished from his own alms-bowl. She however, was lacking in fortune because of her former bad deeds. She was not agreeable to Mahākāla, and so he did not stay with her, did not love her, and did not protect the Teachings either. She therefore became depressed, and in order to enthrall Mahākāla this Kurukullā compendium was taught. From then on, her fortune became vast and excellent. For that reason, children of noble family, if you wish to enthrall sentient beings you should familiarize yourselves with this mantra and this manual of instructions.
3️⃣
It also came to pass that Sunanda’s son was born handsome and good looking, athletic and in possession of auspicious marks, and yet nevertheless dull-witted.
Sunanda therefore asked the Blessed One, “O Lord, my son was born handsome and good looking, athletic and in possession of auspicious marks, and yet nevertheless dull-witted. How, O Lord, may he develop insight? Lord, if this child becomes literate he shall become a protector of your doctrine.”
Upon hearing this, the Blessed One, with words preceded by mindfulness, spoke this manual of practice and gave this mantra. As soon as he had done so, Sunanda’s son, Rohiṇīkumāra by name, acquired insight. By the twelfth year he was free from being intimidated by any of the treatises, as he was thoroughly acquainted with all of the crafts and arts. Therefore, children of noble family, in order to accumulate great insight, you should study this very mantra and its manual of practice.