Here's the breakdown of the idiom's origin:
* Bats' nocturnal lifestyle: Bats are active at night, which may have contributed to the misconception that they are blind. People might have associated darkness with blindness.
* Echolocation: Bats use echolocation, a system of sound waves and echoes to navigate and hunt, which may have further fueled the misconception. People might have interpreted the lack of visible sight as actual blindness.
* Poor vision: While bats do have eyes, their eyesight is not as sharp as that of other mammals. They rely heavily on echolocation, and their vision is likely used for detecting light changes and recognizing shapes in low-light conditions.
Therefore, the idiom "blind as a bat" is likely a result of a combination of factors: the nocturnal behavior of bats, the misunderstanding of echolocation, and the perception of poor eyesight.
It's worth noting that the idiom is often used figuratively to describe someone who is very unobservant or unaware of their surroundings.