cornerstone

What it means

1. A stone forming the base at the corner of a building.

   Clutch it like a cornerstone Otherwise it all comes down Justify denials and Grip 'em to the lonesome end

   2001, Tool, “The Grudge”, in Lateralus (progressive metal, alternative metal)

2. Such a stone used ceremonially, often inscribed with the architect's and owner's names, dates and other details.

   The cornerstone on the Flatiron Building is set on the Fifth Avenue facade.

3. figurativelyThat which is prominent, fundamental, noteworthy, or central.

   Exceptional service is the cornerstone of the hospitality industry.

   2 more examples

   That is the cornerstone of any meaningful debate about budgets and projects, regulations and policies.

   Jewish immigrants came together with other foreign-born groups in organizations like the Industrial Workers of the World, helping to create one of the cornerstones of the American left.

   2019 July 15, Greg Afinogenov, “The Jewish Case for Open Borders”, in Jewish Currents, number Summer 2019

In a sentence

Clutch it like a cornerstone Otherwise it all comes down Justify denials and Grip 'em to the lonesome end

2001, Tool, “The Grudge”, in Lateralus (progressive metal, alternative metal)

Where it comes from

1. Middle Englishcorner ston
2. Englishcornerstone

From Middle English corner ston; equivalent to corner + stone. The figurative sense is in part after Psalm 118:22, and is also quoted several times in the New Testament.