Vedānta was originally a word used in Hindu philosophy as a synonym for that part of the Veda texts also known as the Upanishads.
It is also speculated that “Vedānta” means “the purpose or goal [end] of the Vedas“. Vedanta can also be used as a noun to describe one who has mastered all four of the original Vedas.
By the 8th century, the word came to be used to describe a group of philosophical traditions concerned with the self-realisation by which one understands the ultimate nature of reality (Brahman).
Vedānta is not restricted or confined to one book and there is no sole source for Vedāntic philosophy.