Short answers, pulled from the story.
The word angel arrives in modern English from Old English engel and Old French angele, which derive from Late Latin angelus borrowed from Late Greek angelos. The literal meaning of angelos is messenger, with its earliest form being Mycenaean a-ke-ro attested on Bronze Age clay tablets.
The idea of angels as embodiment of good emerges only under influence of Zoroastrianism where holy entities called Aməša Spənta battle forces conceived as evil by Ahura Mazda. Fravashi function as guardian angels for Zoroastrians since the 19th century appearing as individualized warriors descending to aid those who summon them against demons.
Augustine of Hippo clarified that the term angel refers to the name of their office rather than their nature stating if you seek the name of their nature it is spirit. Gregory of Nazianzus thought that angels were made as spirits and flames of fire following Hebrews 1 while Thomas Aquinas later stated they were created instantaneously by God in a state of grace at the same time when he created all contents of the corporeal world.
Classical period Islamic theology usually distinguishes between three types invisible creatures: angels djinn and devils. Imam Abu Hanifa categorized angels into Illiyyûn Mukarrebûn those around God throne Mudabbirât carrying laws nature and Rasūl messengers.
The earliest known representation angels with wings Prince's Sarcophagus attributed time Theodosius I 379-395 discovered Sarigüzel near Istanbul 1930s. From that period Christian art represented angels mostly wings cycle mosaics Basilica Saint Mary Major 432-440 showing four and six-winged angels derived from Persian art.