“Blood is thicker than water” usually means family comes first—but the phrase has a layered history.

It likely comes from the German proverb “Blut ist dicker als Wasser”, suggesting that family ties are stronger than other relationships. But older versions tell a different story. A 12th-century text by John of Salisbury includes the line “The blood of the covenant is thicker than the water of the womb,” implying that chosen bonds—like friendships or alliances—can be even stronger than family.

By the 19th century, the modern version had taken hold, popularized in part by Sir Walter Scott in Guy Mannering.