bedrock

The word "bedrock" is a transparent compound formed from two native English words of Germanic origin. "Bed," from Old English bedd, originally meant a sleeping place but extended metaphorically to mean any flat base or foundation, as in a riverbed. "Rock," from Old English rocc (via Old French roque), denotes solid stone. The term emerged in the early 19th century in geology to literally describe the solid rock beneath superficial deposits. Its logic is straightforward: the "rock" that serves as the foundational "bed" or substrate. This literal sense was quickly adopted figuratively to describe the fundamental, unshakable principles underlying an idea or system, completing its journey from a concrete geological term to an abstract metaphor for stability.

Structure: bed + rock - bed (Old English): A base, foundation, or supporting layer. Functional role: Modifier, indicating the foundational or underlying nature. - rock (Old English): A large mass of stone. Functional role: Head noun, indicating the core material.