avoir du sang de navet
“avoir du sang de navet” means literally “to have turnip blood.” It really means to lack vigor or courage. The inside of a turnip is white and its juice is also white. Red blood is strong, courageous blood. It gets its redness from the iron it contains. So to have white blood, like the inside of a turnip, is to be anemic, weak and lacking in strength.
This expression first appeared at the start of the 20th century, but it may be connected to an 18th century saying “n’avoir pas de sang dans les veines.” That meant a low energy person, someone who “has no blood in their veins.”
Equivalent English expressions include “to be lily-livered” or “to be spineless.”