hens' teeth

Something very scarce (because hens have no teeth). Typically used in phrases like "rarer than hens' teeth." I can hardly believe your brother got an A on his final exam—grades like that are rarer than hens' teeth for him!

Common Names:

Name	Pronounced	Usage
Rosabel	-	English (Rare)
Warwick	WAWR-ik, WAHR-ik	English (Rare)
Charlton	KAHRL-tən, CHAHRL-tən	English
Anselme	-	French
Dorina (1)	do-REE-nah	Romanian
Selena	-	Spanish, Russian, Greek Mythology (Latinized)