the long piece of wood or steel along the bottom of a ship, on which the frame is built, and which sometimes sticks out below the bottom to help it to keep steady in the water and prevent it from falling on its side （船的）龙骨 Word OriginMiddle English: from Old Norse kjǫlr, of Germanic origin.
Idioms
on an even keel
living, working or happening in a calm way, with no sudden changes, especially after a difficult time （生活、工作等经历困难后）平稳下来，顺顺当当 Business is now back on an even keel after the strike. 罢工后，企业现在恢复平稳。 Setting her life back on an even keel after their break-up had been incredibly difficult. 分手后，让她的生活恢复平稳，这是非常困难的。