涙を流す。

The word 涙 (namida) meaning 'tears' is a compound of 涕 (na), an ancient word for 'fluid from the nose or eyes' (related to 鼻 (hana) for nose), and 水 (mizu) meaning 'water'. Over time, 涕 (na) evolved into 涙 (namida). The verb 流す (nagasu) means 'to shed', 'to make flow', or 'to pour'. So, literally, 涙を流す means 'to shed tears' or 'to make tears flow'. The expression has been used in Japanese literature and daily conversation for centuries to describe the act of crying. Its usage can be traced back to classical Japanese texts, where emotional expressions were often described with vivid imagery. The combination of these two words creates a clear and direct phrase for expressing the act of crying, which is easily understood across different contexts and emotional intensities.