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
Kenrick	KEN-rik	English (Rare)
Tom (1)	TAHM (English), TAWM (Dutch)	English, Dutch
ZİYnet	-	Turkish
Kipling	KIP-ling	English (Rare)
Ash	[æʃ]
Ghoncheh	-	Persian