열이 내리다

This idiomatic expression is composed of two main parts: '열 (yeol)' meaning 'fever' or 'heat', and '내리다 (naerida)' meaning 'to go down,' 'to descend,' or 'to drop.' 1. **열 (yeol):** The noun '열' originates from Middle Korean 'ᄠᅳᆯ (tteil)', which meant 'heat' or 'fever'. Over time, the pronunciation evolved to '열'. It is also related to the character '熱' (열), which means 'heat' or 'fever' in Sino-Korean vocabulary. In this context, it specifically refers to the elevated body temperature associated with illness. 2. **내리다 (naerida):** The verb '내리다' is a common native Korean verb with a broad range of meanings, including 'to come down', 'to fall', 'to descend', 'to drop', 'to get off (a vehicle)', 'to be lowered', etc. Its usage here signifies the reduction or subsidence of the '열' (fever). **Combination:** When '열' and '내리다' are combined, '열이 내리다' literally translates to 'fever descends' or 'fever goes down'. The particle '이 (i)' acts as a subject marker, indicating that '열' is the subject performing the action of '내리다'. This phrase perfectly encapsulates the idea of a fever subsiding or one's body temperature returning to normal after being high due to illness. This expression has been in use for a long time in the Korean language, reflecting a straightforward and natural way to describe the medical phenomenon of a fever resolving. Its etymology is quite transparent, being a direct combination of words describing the state ('fever') and the change ('going down').