The word 忍耐 is formed through the conceptual merging of two deeply related ideas of endurance. The first character, 忍, depicts a blade (刃) over the heart (心), visually symbolizing the inner act of bearing emotional or physical pain without yielding. The second character, 耐, whose ancient form involves the concept of enduring a tedious process (originally related to removing facial hair), extends this idea to signify patient, persistent tolerance of external circumstances over time. Together, they create a compound where 忍 emphasizes the internal, heart-level forbearance of suffering, while 耐 stresses the outward, durable capacity to withstand prolonged hardship, forming a complete picture of steadfast endurance.