Blood is thicker than water

In modern society, the proverb "blood is thicker than water" is used to imply that family relationships are always more important than friends.

The equivalent proverb in German (originally: Blut ist dicker als Wasser), first appeared in a different form in the medieval German beast epic Reinhart Fuchs (c. 1180; English: Reynard the Fox) by Heinrich der Glîchezære. The XIII-century Heidelberg manuscript reads in part, "ouch hoerich sagen, das suppebluot von wazzer niht verdirbet" (lines 265-266). In English we read, "I also hear it said, kin-blood is not spoiled by water."

In 1412, the English priest John Lydgate observed in Troy Book, "For naturally blood will be of kind / Drawn-to blood, where he may it find."

By 1670, the modern version was included in John Ray's collected Proverbs, and later appeared in Sir Walter Scott's novel Guy Mannering (1815): "Weel — Blud's [sic] thicker than water — she's welcome to the cheeses." and in English reformer Thomas Hughes's Tom Brown's School Days (1857).

The phrase was first attested in the United States in Journal of Athabasca Department (1821)." On June 25, 1859, U.S. Navy Commodore Josiah Tattnall, in command of the American Squadron in Far Eastern waters, made this adage a part of American history when explaining why he had given aid to the British squadron in an attack on Taku Forts at the mouth of the Pei Ho River, thereby infringing strict American neutrality.

Authors Albert Jack and R. Richard Pustelniak claim the original meaning of the expression was that the ties between people who've made a blood covenant were stronger than ties formed by "the water of the womb".

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