Bheeshm is a very important character of Mahaabhaarat. There was a king of Hastinaapur named Shaantanu. Once he went for hunting that he saw a beautiful young girl named Gangaa. He got attracted to her and asked her to marry him. She got ready to marry him but on two conditions, one that Shaantanu would never ask her what and why she was doing; and two, the day he would ask her she would reply his question and leave him for good. Shaantanu agreed and they got married.

After some time Gangaa had a son. All got very happy to hear the news that now Hastinaapur had got its Crown Prince. Shaantanu had no limits of his happiness. But soon he plunged into the sea of grief when he saw that Gangaa was taking his son towards Gangaa River. He followed her for his curiosity sake, but he was stunned to see that she drowned him in the river. According to Gangaa's condition he could not ask her what and why she was doing that? She did the same with his next six sons. Everybody was talking about Raajaa that why Raajaa does not ask her about his sons.

Now she was to give birth his eighth child. This time also she gave birth to a son and as usual she took him to Gangaa River. But this time the King could not resist himself and asked her - "Gangaa, Why are you doing this to my sons? No mother does this to her children." Gangaa told him that she was living with him because of a curse and as he had asked her this question, now she is free from this curse, so she has to go. She told him that these children were also born to her because of Shaap. So she did not kill them rather she freed them from the Shaap. Since this child was still very young, she would take him with her, educate him and bring him back to the King when he would be worthy of becoming Crown Prince. She named him Devadatt. And she went away with the prince. Raajaa again plunged into the sea of grief, but could not do anything.

Some years passed, that one day King heard that a young boy has stopped Gangaa's water with his arrows. He got surprised to hear this and went to see who was such a skilled boy. When he came to the boy face to face, He saw Gangaa coming towards him. She introduced him to his father, handed him over to him and went away. Shaantanu declared him the Crown Prince.
x   ~   x   ~   x   ~   x   ~   x   ~

Again some time passed and once again the similar situation arose before Shaantanu. Once Shaantanu went for hunting that he saw a beautiful girl who used to take passengers from this bank of Yamunaa to the other bank of Yamunaa. He fell in love with her. She was a fisherman's daughter. Her name was Satyavatee. Her father knew that she would live in palace but he did not know in whose palace. Shaantanu decided to propose for her, so he went to Daash Raaj (Satyavatee's father) and proposed for her. Satyavatee also loved him but she had no say of her own.

Daash Raaj said - "O King, I have no objection, but her birth chart says that she will rule the kingdom, and I don't see any chance of that, that is why I cannot marry her to you." Since Shaantanu had already declared Devadatt as the Crown Prince of Hastinaapur, he could not say anything and came back to his palace. But he had got lost in Satyavatee's thoughts. He did not come out of his room for several days. Devadatt noticed his condition and asked his ministers etc if anybody knew about its reason. All expressed their ignorance. Then he asked Raajaa's Saarathee (chariot driver) if he knew something about it. He told him the whole story.

Devadatt went to Daash Raaj and asked him why he could not marry his daughter to Shaantanu. Daashraaj told him also what he told Shaantanu also. He said - "I have no objection but Satyavatee's chart says that she would rule the kingdom, and Raajaa has already declared you as that Crown Prince, then her chart does not match with this condition, so  cannot marry her to him." Devadatt said - "I take vow that I leave my status of Crown Prince and I will never ask for kingdom. Only Satyavatee's son will be the King of this kingdom."

Dash Raaj was still not satisfied with this vow, he said - "O Prince, It is all right that you have taken a vow, but what is the surety of your children? If they ask the kingdom after they grow up, then?" At this Devadatt took another vow - "I Devadatt take this vow that I will never marry my whole life, I will never have my own children, I will always live as a bachelor and I will die as a bachelor." and asked him - "Now O Daash Raaj, Is there any more problem in your mind?" There was no problem now so Devadatt took Satyavatee to Hastinaapur.

Because of taking this great vow, he was named as Bheeshm. Bheeshm means great and very difficult. Because he took such a great and very difficult vow, he was named as Bheeshm. He got so popular by this name that people forgot his original name. When Bheeshm brought Satyavatee home, Shaantanu got very angry but got moved too seeing his respect and love towards himself. He bestowed him a boon of Ichchhaa Mrityu, that Death would not come to him itself until he wishes for it.