In the Bible "manna" is the food that God provides for the Israelites in the wilderness after the Exodus; the name itself comes from their reaction when they first see it, recorded in Exodus 16.
Exodus 16:15 in the King James Version reads:
And when the children of Israel saw it, they said one to another, It is manna: for they wist not what it was. And Moses said unto them, This is the bread which the LORD hath given you to eat.
The verse appears in Exodus 16, in the account of the first appearance of manna in the wilderness of Sin. Read it in context at Exodus 16:15, or the full chapter at Exodus 16. Encyclopedia entry: en.wikipedia.org/wiki/Manna.