What is the origin of the idiom "lost in the mists of time" and when to use it?

The idiom "lost in the mists of time" suggests that something has become exceedingly difficult to remember or recall due to the vast amount of time that has passed since it occurred. The expression likely draws upon the idea that memories, like distant objects shrouded in mist, become obscured and unclear as they recede further into the past. This idiom is often used when discussing events or details that occurred so long ago that they have faded from one's memory or become hazy and indistinct.