underpinning
UK: ˌʌndəˈpɪnɪŋ | US: ˌʌndərˈpɪnɪŋ
n. a support or foundation, especially one beneath a structure
n. (figurative) a basis or justification for something
vt. the act of providing structural or ideological support
The word "underpinning" combines "under" (Old English under, meaning "beneath") and "pin" (Old English pinn, meaning "peg" or "fastener"), originally referring to physical supports beneath a structure. The suffix "-ing" nominalizes the action or result. Over time, it expanded metaphorically to describe foundational principles or justifications. The logic mirrors construction: just as beams underpin a building, ideas underpin arguments.
The bridge's steel girders serve as its underpinning.
Democracy relies on the underpinning of free speech.
Engineers inspected the underpinning of the historic tower.
Her theory lacks a solid philosophical underpinning.
The report exposes the economic underpinnings of the conflict.