Today’s idiom: blood is thicker than water
Meaning: modern meaning – family bonds are stronger than non-familial ones
Origin: It seems that the meaning of the phrase has changed a lot since this phrase first came about, though the phrasing is not the same. The original phrase: “Blood is not spoilt by water” was written in 1180 by Heinrich der Glîchezære in Reynard the Fox. It is thought that the meaning here is the opposite of our modern meaning, referring to a covenant made by the shedding of blood, whether that is an actual blood ritual or the common bloodshed that occurs in times of war amongst soldiers. It first appeared in its modern phrasing in 1670 in John Ray’s Proverbs and again in 1815 in Sir Walter Scott’s Guy Mannering. It is unclear when its meaning changed to where it stands now, though it might have been in the 1900’s.