The story
From ascend + -ancy or ascendant + -cy. The use in ecology is due to Robert Ulanowicz.
First known use, by meaning
- from 1986 A quantitative attribute of an ecosystem, defined as a function of the ecosystem's trophic network, and intended to indicate its ability to prevail against disturbance by virtue of its combined organization and size.
Etymology from Wiktionary, CC BY-SA 4.0.