What is the origin of the idiom "rack one's brain" and when to use it?

The origin of the idiom "rack one's brain" is believed to be derived from the medieval torture device known as the "rack." The rack was a mechanical contraption used to stretch or torture individuals by applying extreme tension to their bodies. The phrase represents the mental strain and anguish that one experiences when trying to recall or solve something difficult, similar to the physical agony inflicted by the rack. It is commonly used when someone is faced with a challenging problem, a difficult riddle, or the need to recall specific information from memory.