There is no mention of Khidhr in the Bible, and it is unlikely to find mention of his name or anything related to him in any other books of Christianity. Of course, you should also know that in the holy Quran the specific name of “Khidhr” is not mentioned. The only thing mentioned is his wisdom and servitude to Allah (swt).[1] However, in many traditions, this wise man is introduced as “Khidhr”.[2] From some of the traditions, it is understood that his real name was “Talia Bin Malakan Bin Aber Arafkhasht Bin Sam Bin Nuh”[3] and Khidhr is his nickname[4] because wherever he stepped would become green and thriving.[5]
[1] Kahf:65 عَبْداً مِنْ عِبادِنا آتَیْناهُ رَحْمَةً مِنْ عِنْدِنا، وَ عَلَّمْناهُ مِنْ لَدُنَّا عِلْماً
[2] Allamah Majlisi, Biharul-Anwar (translation of Muhammad Baqir Kamare’i), vol. 8, pg. 217.
[3] See translation of Al-Mizan,vol. 13, pg. 584.
[4] Allamah Hilli, Alfein (translation of Vujdani), pg. 1009.
[5] Biharul-Anwar, vol. 8, pg. 202.