An English expression meaning 'to undergo great hardships', or 'to face great danger'.
This may or may not come from the ordeal by fire and the ordeal by water, both used to test for guilt in the Middle Ages. In the ordeal by fire, a man was made to hold or walk on red-hot iron. After three days, the wound was inspected, and if it had healed over, the man was innocent. The ordeal by water worked the same way; the arm was plunged into boiling water, and after three days examined, etc. There was also the ordeal by cold water, in which the person being tried would be bound, and dropped in to a body of water. If they sunk to a certain depth, they were innocent; if they did not sink, they were guilty.
The account I give above is the more common one (in my experience, anyway), but liveforever has almost certainly found the source that put this phrase into common usage.