heart of oak

A trait said to belong to a very emotionally and/or mentally strong person. I don't know how a soldier does it—he or she must have a heart of oak. My brother has a heart of oak and has remained totally calm while coping with his wife's sudden illness.

Common Names:

Name	Pronounced	Usage
Diane	dee-AHN (French), die-AN (English)	French, English
Viona	-	English (Rare)
Azrael	-	Judeo-Christian Legend
Shanice	shə-NEES	African American (Modern)
Dar	-	Hebrew
Simin	-	Persian