Orunmila went to Ootu Ife kingdom when the King of Asedo sent for him to come divine for him and the town's people in need of spiritual works. Orunmila then sent for three priests to divine for him: 

Obara Egun tan 
Egun pin
Pin pin pin lomo odo segun

Ifa divination was performed for Orunmila the day he was going to the city of asedo to do spiritual works. The Ifa priest told him to perform a sacrifice so that all he did at Asedo would be successful. Orunmila performed the sacrifice. The priest also gave him a warning not to reject anybody and that there was a woman in Asedo who he should not neglect. 
After a while, Orunmila went to Asedo. As he was about to enter the city, it began to rain. This rain was so heavy that Orunmila had to stop in the bush before entering the city. He found a hut but did not see the owner. Orunmila entered and found only a woman inside. 
This woman was very kind: She took care of Orunmila. She prepared food for him. She removed his wet clothes to dry. As the rain had not subsided before dark, Orunmila agreed to stay overnight in the hut with the woman. The woman was happy to receive Orunmila. She went on to explain to Orunmila that she had no husband to share the hut with her and this was her biggest concern. She begged him to be her husband. 
Orunmila agreed and they slept until the following morning. Orunmila was ready to leave when, in the light of day, he was finally able to see the woman more clearly. She was a leper. He thanked her for her hospitality and promised to help her whenever he could. 
Orunmila departed and proceeded to the palace of Asedo. The King received him warmly and he was given a special guest room. He started to work for the people, the chiefs, the rich and poor alike. Orunmila remained in Asedo for several years, performing successful works. Orunmila became prosperous in Asedo. 
Every Ose Ifa, he would accompany his priests to the palace to divine for the King and offer him spiritual direction. One day, as Orunmila and the priests were leaving the palace, a leperous woman approached him. She recognized Orunmila in spite of his elaborate clothes and crown. She held onto Orunmila and reminded him of his promise to help her whenver he could. Orunmila's entourage of priests were offended by the leper and wanted to fight her. When she tried to touch his clothes, they chased her away. But Orunmila accepted her outreach and asked her to state her concerns. 
She cried, "You are my husband! You rejected me!" Orunmila asked her to explain when this had happened. She reminded him of his arrival in Asedo, that rainy night. Now Orunmila remembered: "You were the leper!" She replied, "Yes." Orunmila asked her to follow him and and divined for her. Orunmila prepared medicine for her and cured her leprosy. 
From that time onward, she lived with Orunmila and gave him many children, most of whom were girls. When they grew up, they were married to Babalawo, one by one. When the Ifa priests asked Orunmila why it was this way, he explained that "The-child-that we-cured-her-mother's-leprosy" should be called APETEBII (Apa-ete-bii).
Since then, all Ifa priest's wives are called Apetebii and sometimes, before a lady marries a Babalawo, she is called Iyawo Ifa. But once she is married, we call her APETEBII. 

REFERENCE: Holy Odu ObaraOgunda

Aboru aboye abosise. 

Elebuibon, Ifayemi. Apetebii. Page 28-29