Definition & Meaning of "[whistle] in the dark"

What is the origin of the idiom "whistle in the dark" and when to use it?

The idiom "whistle in the dark" has its origin in the idea of using sound to dispel fear or create a sense of comfort in the darkness. The phrase metaphorically refers to an act of feigning bravery or confidence in a situation that is uncertain, dangerous, or unsettling. Just as someone might whistle to alleviate their fear when walking alone in the dark, "whistle in the dark" implies putting on a brave front or attempting to maintain optimism in the face of uncertainty or adversity.