not judge a book by its cover

to not be able to really know about someone or something by simply looking at them She doesn't look very bright, but you can't judge a book by its cover.

Common Names:

Name	Pronounced	Usage
Tighe	-	Irish
Emory	['eməri]
Wilhelmina	[.wilə'mi:nə]
Mansel	-	English (Rare)
Winnie	WIN-ee	English
LucÍA	loo-THEE-ah (Spanish), loo-SEE-ah (Latin American Spanish)	Spanish