full-grown

The compound adjective "full-grown" is a transparent combination of two native English elements. "Full," with Proto-Germanic and ultimately Proto-Indo-European roots related to plenitude, intensifies the state described by "grown," the past participle of "grow." "Grow" itself originates from a Proto-Germanic verb meaning "to green, flourish," a sense tied to plant life. The logic of the word is direct and literal: it describes an organism (now extended to ideas or projects) that has completed its process of growth, having reached its mature or final size and development.

Structure: full (complete) + grown (developed) - full: From Old English full, meaning "complete, entire." It functions as an intensifier in this compound, indicating completeness. - grown: The past participle of the verb grow, from Old English grōwan, meaning "to flourish, increase, develop." It functions as the core element describing the state of development.