Before being named Tegh Bahadur, the name of the future 9th Guru was Tiag Mal.
When Guru Hargobind Sahib Ji noticed Tiag Mal at a young age that he had an extraordinary ability to use the Kirpan. He noticed the excellent use of the sword and skill from his son. After seeing such talent, he named his son from Tiag Mal to Tegh Bahadaur standing for the great ability to use the tegh (sword)
Old texts record that Tegh Bahadur took part in the battle of Kartarpur on April 26, 1635.
This was the last major conflict his father, Guru Hargobind, had to engage in.
According to the Sri Gur Pratap Suraj Granth, Tegh Bahadur, riding his horse, made bold sallies in all directions. Mata Nanaki and her daughter-in-law watched his feats of arms from the top of their house. When word was sent to him to retire, he, like his brothers, answered that it was not proper to turn one’s back on the battlefield. Tegh Bahadur was then fourteen years old.
After the battle of Kartarpur, Guru Hargobind, Nanak VI, went to live at Kiratpur.
For Tegh Bahadur this meant nine years of uninterrupted happiness in the company of his father. As was his wont, “he remained always saturated in the remembrance of God and spoke but little.” When his time Gurdwara Baba Bakala at City of Bakala District Amritsar, place of Guru Tegh Bahadur ji came near, Guru Hargobind asked Nanaki to go and live in the village of Bakala.
Guru Hargobind appointed his elder son, Guru Har Rai as next guru. Tegh Bahadur and his brothers were present at this occasion.
Tegh Bahadur and his wife Mata Gujari ji shifted to Bakala.
It was at Bakala when he heard about the passing away of Guru Har Rai and appointment of Guru Har Krishan as Nanak Eight.
It was also at Bakala when he heard about his appointment as ninth guru through Makhan Shah and other Sikhs.