the council seems to be where the idea of trinity originated from.
The Nicene Creed introduced the word "homoousious" or "consubstantial" meaning "of one substance." This word was not invented at the Council. Eusebius writes that some of the "most learned and distinguished of the ancient bishops had made use of consubstantial in treating of the divinity of the Father and the Son" (See document E in the Appendix, Baker). We do not have the sources that Eusebius must have had regarding the use of this word. Today, the only source is Origen who used the word in what seems the orthodox way (Johannes Quastren, "Patrology," Volume 2, p78). However, this phrase of Eusebius stands as a witness to the existence of wider use.
The bishops assembled at Nicea were careful to explain how they used the word, and what it meant. This is because it had been misused by Paul of Samosta. Regarding this unorthodox usage, St. Hilary and St. Basil say that it was said to be "unfit to describe the relation between the Father and the Son" at a council that met in Antioch (Ibid, p14). Apparently Paul of Samosta applied the word in a manner that implied division of nature, as several coins are from the same metal (Baker, p21).
Alexander of Alexandria had called a meeting of the presbyters [priests]. According to the historian Socrates, the aging "pope" [some early senior bishops were called "papa," that is, "father"] "with perhaps too philosophical minuteness" began to lecture on the theological mystery of the Holy Trinity. Alexander had been discussing the Father, the Son, and the Holy Ghost for some time when he was interrupted by one of the presbyters called Arius, a native of Libya. There is no evidence that Alexander was a profound theologian. He may have bumbled, and it is possible that Arius was justified in accusing Alexander of Sabellianism, a heresy that involved a belief in the unity of God at the expense of the reality of the Trinity. But in combating Alexander, Arius fell into a new heresy, for he announced, "If the Father begat the Son, then he who was begotten had a beginning in existence, and from this it follows there was a time when the Son was not". Here, at some time in 319, the cry of the Arians--"There was a time when the Son was not"--was first heard. The words were to have an extraordinary influence on the shaping of the church. They were dynamite and split the church in two, and these words, which read in Greek like a line of a song, still echo down the centuries.