한 귀로 듣고 다른 귀로 흘리다.

The idiom '한 귀로 듣고 다른 귀로 흘리다' (han gwireo deutgo dareun gwireo heullida) literally translates to 'to hear with one ear and let it flow out through the other ear.' This phrase succinctly captures the image of information entering one ear and immediately exiting the other, signifying that the information is not being processed or retained. While the exact historical origin of this specific Korean idiom is not readily documented with a precise '200+ words origin history,' its conceptual roots can be traced to universal human experiences and expressions across various cultures that convey the idea of inattention or disregard. Many languages have similar idiomatic expressions that use the metaphor of ears to denote listening or ignoring. For example, English has 'in one ear and out the other,' which carries the identical meaning. The concept itself likely emerged from observations of how people sometimes selectively listen or consciously choose to disregard certain information, leading to the development of vivid metaphorical language to describe such behavior. The phrase is a common and intuitive way in Korean to express the act of not internalizing what is being said, often implying a lack of interest, skepticism, or deliberate dismissal of the information.