Meaning: A showy article is not necessarily valuable.

Origin: The 12th century French thelogian Alain de Lille wrote "Do not hold everything gold that shines like gold" and in 1553 Thomas Becon used in The relikes of Rome: All is not golde that glistereth.

By using this idea in The Merchant of Venice, 1596, Shakespeare made it well-known.

MOROCCO:
O hell! what have we here?
A carrion Death, within whose empty eye
There is a written scroll! I'll read the writing.
All that glitters is not gold;
Often have you heard that told:
Many a man his life hath sold
But my outside to behold:
Gilded tombs do worms enfold.
Had you been as wise as bold,
Young in limbs, in judgment old,
Your answer had not been inscroll'd:
Fare you well; your suit is cold.
Cold, indeed; and labour lost:
Then, farewell, heat, and welcome, frost!
Portia, adieu. I have too grieved a heart
To take a tedious leave: thus losers part.