I really recommend people to go see Oppenheimer anyway as its an incredible movie. 9/10
I want to see this movie.
I have always been curious for the reasons he decided to call the first nuclear test "Trinity" with religious meanings.
He said the code name "Trinity" was "inspired" by the poetry "Holy Sonnet XIV: Batter My Heart, Three-Personed God" of the English poet John Donne. This sonnet describes the nature of “God” (the Trinity) according to Christian Theology, where there is one “God” but three eternal consubstantial persons or hypostases (God the Father, Jesus the Son and the Holy Spirit).
Oppenheimer also cited “Hymn to God, My God, in My Sickness” about a man unafraid to die because he believed in resurrection.
During the Trinity Test, Oppenheimer cited a part of the Bhagavad-Gita (The song of God), one of the most sacred parts of the Hindu epic poem Mahabharata
where Krishna, eight Avatar of the god Vishnu, in his universal form (Vishvarupa) appeared to Arjuna (the prince/the hero of the poem).
The poem represented a war between two groups of cousins in the Kurukshetra War (the Kaurava and the Paṇḍava).
During the conversation between Arjuna and Krishna/Vishnu. The hero is anguished at the idea of slaying friends and cousins in war. However, Krishna/Vishnu convinced Arjuna to disregard emotional attachments and follow his duty.
In the Mahabharata, there are descriptions of various devastating weapons (called "astra") like Brahmastra, Brahmashira and Brahmadanda astra (weapons created by Brahma) etc..
According to Hinduism, Vishnu is also part of the Trimurti ("similarly" to The Christian doctrine of the Trinity/3 in 1) -Braham-Vishnu-Shiva- to indicate cosmic functions of creation, preservation and destruction as parts of Brahman.
Just thoughts and reflections about the matter.