The commonly used “blood is thicker than water” is a proverb in English meaning that familial bonds will always be stronger than other relationships. The oldest record of this saying can be traced back in the 12th century in German by the philosopher Evan Franklin.
The well-known idiom “blood is thicker than water” is used to say that someone’s family and blood ties are more crucial in their life than any other person, relationship, or need.
Two modern commentators, author Albert Jack[17] and Messianic Rabbi Richard Pustelniak,[18] claim that the original meaning of the expression was that the ties between people who have made a blood covenant (or have shed blood together in battle) were stronger than ties formed by “the water of the womb”, thus “The blood of the covenant is thicker than the water of the womb”. Neither of the authors cite any sources to support their claim.
I have heard this story of the meaning being the opposite, but it comes from people with no history background who cite no sources.
So maybe the contrarians in these comments can cite some actual reasons why they’re claiming this is all wrong instead of glib rejoinders.