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
Giovannetta	-	Italian
Elfreda	-	English
Kleopatros	-	Ancient Greek
Graciano	grah-THYAH-no (Spanish), grah-SYAH-no (Latin American Spanish), grə-SYA-noo (Portuguese)	Spanish, Portuguese
Rutherford	['rʌðəfəd]
Inigo	IN-i-go	English (Rare)