To make an extraordinary effort or go to great lengths to help someone or accomplish something, often involving personal sacrifice or inconvenience.
This phrase originated from the physical impossibility and extreme difficulty of literally bending one's spine backwards to a significant degree. First appearing in American English around the 1920s, it evolved from earlier expressions about physical contortions representing extreme effort, emphasizing how far someone will go by describing an anatomically challenging position.
The genius of this idiom lies in its physical impossibility - most people literally cannot bend over backwards without falling down, making it the perfect metaphor for attempting something that seems beyond normal human capability. It captures both the admirable dedication and the potential foolishness of extreme accommodation.
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