تعریف و معنای "[hold] the key to {sth}"

What is the origin of the idiom "hold the key to something" and when to use it?

The origin of the idiom "hold the key to something" is not tied to a specific historical event or cultural reference. It is a metaphorical expression that has evolved over time based on the literal concept of keys and their role in unlocking or accessing locked spaces or objects. As language developed, this literal meaning was extended metaphorically to represent knowledge, information, or control that is essential for understanding or resolving a situation. This expression is used when emphasizing the significance of possessing crucial insights or understanding that can influence the outcome or direction of a situation.