E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The chief cornerstone. A large stone laid at the base of a building to strengthen the two walls forming a right angle. These stones in some ancient buildings were as much as twenty feet long and eight feet thick. Christ is called (in Eph. ii. 20) the chief corner-stone because He united the Jews and Gentiles into one family. Daughters are called corner-stones (Psalm cliv. 12) because, as wives and mothers, they unite together two families. In argument, the minor premise is the chief corner-stone.