1.
formation, origin, how something came to be
The process or history by which something was formed or established. Often used when explaining how a word, organization, or concept originated.
2.
structure, composition, makeup
The way something is composed or made up of its constituent parts.
成り立ち is the noun form derived from the verb 成り立つ (to be established, to consist of). It refers to either how something came into being or what something is made up of.