The story
In reference to any of several places in the Bible where "a peculiar people", a people set apart from others, is mentioned, such as Deuteronomy 14:2, 1 Peter 2:9, and Titus 2:14: for example, "For thou art an holy people unto the Lord thy God, and the Lord hath chosen thee to be a peculiar people unto himself, above all the nations that are upon the earth" (Deuteronomy 14:2).
Etymology from Wiktionary, CC BY-SA 4.0.