Short answers, pulled from the story.
Scholars propose that the name Metatron derives from Hebrew words meaning to guard or protect, Greek terms meta and thronos indicating service behind a throne, or Latin metator signifying messenger. Philip Alexander suggests it may be a magical term found in Hekhalot literature and Merkabah texts like 3 Enoch.
The identification of Enoch with Metatron appears first in 3 Enoch also known as the Book of Enoch where Enoch transforms into the angel after being assumed into Heaven. Early kabbalists assumed this connection even though it is not explicitly made in the Talmud.
The Babylonian Talmud mentions Metatron by name in three specific places: Hagigah 15a, Sanhedrin 38b, and Avodah Zarah 3b. These passages describe events such as Elisha ben Abuyah seeing Metatron sitting in Paradise and Rabbi Idith hearing about Metatron's role as a messenger.
Scholars note that the Talmud states Metatron received sixty strokes with fiery rods to prove he was an angel who could be punished unlike a deity. This punishment occurred because Elisha ben Abuyah saw Metatron sitting down which is unusual for anyone in the presence of God without special permission.
The earliest account of Metatron within Islamic scriptures might derive directly from the Quran itself where Surah 9:30 and 31 mention Uzair venerated as Son of God. Al-Suyuti identifies him specifically as the angel of the veil knowing what lies beyond it while Ahmad al-Buni describes Metatron wearing a crown and lance in magical works.