From Latin derivare (to draw water from a stream), from rivus (brook) — something channeled from a source, like water diverted from a river
A financial instrument whose value is derived from the performance of an underlying asset, or something that is based on or developed from another source
From Late Latin 'derivativus' meaning drawn off, from Latin 'derivare' meaning to lead or draw off water (from a stream), from 'de-' (from, away) and 'rivus' (stream). The original image is of diverting water from a river into a channel — creating something that flows from a source but is separate from it. The word was applied to grammar (a word derived from another), mathematics (a function derived from another), and finally finance (an instrument
The word rival comes from the same Latin root rivus (stream). Latin rivalis originally meant a person who uses the same stream — a neighbor sharing water rights. Disputes over water access were so common in the Roman countryside that sharing a stream became synonymous with competition. Derivative and rival are etymological cousins