The word 发泄 is formed through a vivid conceptual metaphor where the first character 发 (to emit, release) initiates the action, and the second character 泄 (to discharge, leak out) completes it by depicting the nature of the release; together, they create a compound that visually and notionally represents the idea of venting or letting out pent-up internal pressures, much like opening a sluice gate to allow built-up water to flow forcefully away.