The names of relationships between nodes model the kinship terminology of family relations.
The gender-neutral names "parent" and "child" have largely displaced the older "father" and "son" terminology.
Also, "encyclopedia", as the root of the tree, is the ancestor of "science", "culture", "art" and "craft".
The Oxford English Dictionary records use of both the terms "tree structure" and "tree-diagram" from 1965 in Noam Chomsky's Aspects of the Theory of Syntax.
For a formal definition see set theory, and for a generalization in which children are not necessarily successors, see prefix order.