(as|) sound as a roach
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free from illness or injury
The idiom "sound as a roach" is thought to have originated in the 18th century. It is believed to be a reference to the fact that cockroaches are very resilient creatures. They can survive in a variety of harsh environments, and they are very difficult to kill. As a result, they came to be seen as a symbol of good health and vitality.
- After a rigorous workout, Sarah felt as sound as a roach, ready to take on any challenge.
- Despite his age, the elderly man's mind was sound as a roach, with a sharp memory and quick wit.