Select the option that best expresses the meaning of the given idiom.

To get cold feet

The correct answer is: To suddenly lose confidence or courage before doing something.

Explanation and Meaning:
The idiom "to get cold feet" is an informal expression used to describe a situation where someone suddenly becomes nervous, hesitant, or loses their courage/confidence right before undertaking an important event or decision (such as getting married, delivering a speech, or making a major commitment).

Origin & Metaphor:
Metaphorically, when a person experiences extreme fear or anxiety, blood flow can recede from the extremities to vital organs, physically causing cold hands or feet. In figurative language, having "cold feet" symbolizes hesitation or wanting to back out of a plan at the last moment.

Analysis of Options:

1. To display remarkable bravery in a tough situation: Incorrect. This is the opposite of getting cold feet.
2. To ask someone for immediate assistance: Incorrect. Getting cold feet relates to fear/hesitation, not asking for help.
3. To admit defeat in a graceful manner: Incorrect. Admitting defeat usually relates to expressions like "throwing in the towel."
4. To suddenly lose confidence or courage before doing something: Correct. This accurately captures the definition of the idiom.