In our scriptures, there are many personalities who are not known by their real names. Some have some reasons to be known by their other names while others have not. It is really interesting to know about them that how did they come to by their popular names. and not by their real names..
(1) Ved Vyaas
Ved Vyaas Jee has been a great sage of his times. He was the 19th incarnation of Vishnu from among the 24 incarnations. He was the son of sage Paraashar (grandson of Maharshi Vashishth Jee) and a fisherwoman Satyavatee. Paraashar saw Satyavatee and intended to give her a child. In spite of opposiong the idea, as she was an unmarried girl, Paraashar created a smoke all around them and gave her a son. Since he had very dark complexion (Krishn) and was born on an island (Dweep) he was named as Krishn Dwaipaayan. Krishn means dark complexioned and Dwaipaayan is a compound word - Dweep + Ayan. Dweep means island and Ayan means home or dwelling place; sp Dwaipaayan means whose dwelling place is an island.
This Ved Vyaas is not his real name. Later when he divided the Ved, then he was known as Ved Vyaas. Ved means Ved and Vyaas means who has divided; so Ved Vyaas means who has divided Ved. For general information, in every Chatur-Yug - one Sat, Tretaa, Dwaapar and Kali combined is called a Chatur-Yug; in the end of the Dwaapar Yug a Ved Vyaas is born to divide the Ved. This Ved Vyaas was born in 28th Dwaaper Yug. 27 Ved Vyaas have been there before him. Thus Ved Vyaas is not a name but a title for the person who divides the Ved, but he is more popularly by this name only.
Who does not know Bheeshm? Especially after seeing Mahaabhaarat Serial. If you have seen it, you must also be knowing that Bheeshm was not his real name. Then what was his real name? Bheeshm was the 8th son of Raajaa Shaantanu and Gangaa. Gangaa had already freed Shaantanu's 7 sons from birth and death cycle, but this their 8th son had to live on Prithvi. Gangaa named him Devavrat and took him along with her to Swarg to educate him. When he was 16 years old, she handed over him to his father and went back to Swarg.
Shaantanu had only one son and his wife was gone. A fear was in his mind if something happened to his only son...? So he intended to marry again. Fortunately he found that fisherwoman (Ved Vyaas' mother) and got attracted to her, but unfortunately when he proposed to her father her father did not get ready to marry his daughter to him, because he was sure that Satyavatee's children will rule a kingdom, and Shaantanu had already declared Satyavrat his Crown Prince. Hearing this Shaantanu became sad as he coulf not do injustice with his first-born son. He withdrew himself from his royal duties which worried Devavrat.
When Devavrat found his father sad, he went to Satyavatee's father and asked the whole matter. The fisherman told him everything. Devavrat said - "Today I take a vow that I will not claim the throne for my whole life. Now are you ready to marry Satyavatee to my father?" The fisherman said - "Not yet Prince." "Why?" "It is all right that you have given up your rights on the throne, but if your children asked for it, then...?" Devavrat did not take even a moment to decide what he had to do, he took another vow immediately - "I will never marry in my whole life time, I will live alone and die alone, this is my vow." At the same time gods appeared in the sky, showered the flowers on him and gave him the name Bheeshm because of taking such a difficult vow. Thus Bheeshm is not his name, his name is Devavrat but nobody knows his real name. he is known as Bheeshm.
(3) Soot Jee
Soot is also not a name. Soot is word for those children whose father has married a woman whose Varn (Braahman, Kshatriya, Vaishya and Shoodra - these are the four Varn in a Hindu society) is higher than his own, for example if the boy is of Vaishya Varn, and he marries a Braahman girl, their children will be called Soot. This type of marriage is called Vilom (reverse) marriage. Such children did not have much respect in the society because the Vilom marriage was not the prescribed way of marriage. They were not otherwise inferior in any way - they were intelligent but they just did not reach at the right status in the society.
Many Soot may be seen in Mahaabhaarat times - Shaantanu's charioteer Adhirath was a Soot, Dhritraashtra's charioteer was a Soot, Karn being the son of Adhirath was also known as Soot. They were otherwise all intelligent and brave. It mostly happened with kings (Kshatriya) so being a Soot they could not be the prince or king, but they became the charioteer of the kings. They were their friends and counselors too in their depression times. Sanjaya's role in Mahaabhaarat is so crucial.
Such one Soot was a very dear disciple of Ved Vyaas Jee. His name was Romharshan (or Lomharshan). Vyaas Jee noticed his interest in Itihaas (history), so he taught him Mahaabhaarat. And he assigned him to tell Puraan to others on Prithvi. That is why his name is found in most Puraan. His real name appears very rarely, mostly he is described by the title "Soot Jee" and thus nobody knows his real name.
Another Soot Jee - Since he was known as Soot Jee, his son also came to be known as Soot Jee. His son's real name was Ugrashravaa. When Balaraam Jee had killed Romharshan in anger, he was replaced by his son Ugrashravaa who was given all powers and knowledge of Romharshan Jee by Balaraam Jee. Both names, Romharshan and Ugrashravaa, are not known to people.
(4) Shaunak Jee
If you have read Puraan, you must have heard and read the name of Shaunak Jee. There are many stories told and heard by Shaunak Jee. He was the son of sage Shunak Jee that is why he came to be known as Shaunak Jee. His real name was Ghritsamad which is not generally known to people.
This is the name of a King. Can you tell the real name of this King? Or otherwise also, who was he? You must have heard the name of Truth-speaker Harishchandra, Trishanku was his father. So what was his real name - his real name was Satyavrat. Once it came to his mind that he should go to Swarg (Heaven) with his physical body, so he handed over his kingdom to his son Harishchandra and went to forest and started looking for a sage who could send him to Swarg with his physical body. He approached his family priest Vashishth Jee but he refused saying that it was not possible.
By chance, in those days, Vishwaamitra Jee was doing great Tap to compete with Vashishth Jee. When Vishwaamitra Jee heard this, he found an opportunity to test his Tapasyaa and he got ready to send him to Swarg with his physical body. Story is long, and Vishwaamitra Jee succeeded to send the King to Swarg in his physical body. But since it was against the law of nature, he got hung in between the Swarg and Prithvi and he is hung there even today. Since that day he became known as Trishanku. Trishanku means "who is neither here, nor there."
But Trishanku was not his real name. Then what was it? His name was King Satyavrat.
(6) Vishwaamitra Jee
Who does not know Vishwaamitra Jee. His name comes in reference of writing Rig Ved Mantra and Gayatri Mantra, Raam and Lakshman in Raamaayan and Vaalmeeki Raamaayan; Shakuntalaa whose son was Bharat on whose name this country is called Bhaarat; and Truth-speaker Harishchandra, that he tested him in his jealousy with Vashishth. Another strange thing about him that he is not even Rishi, he was a Kshatriya King. He became a Brahmarshi only after doing rigorous tap. He is the only one most known converted Braahman from a Kshatriya. Vishwaamitra Jee is the son of King Gaadhi, and Parashuraam's father Jamadagni's Maamaa.
His real name was also not Vishwaamitra. When he was born he was named Vishwarath. He came to be known as Vishwaamitra later after becoming the Brahmarshi.
See the Real Names-2 also to know the real names of Kali Yug personalities.