The cause of limber tail has always been somewhat mysterious, with anecdotal evidence suggesting it happens more often in larger working dog breeds like Labrador retrievers, and has been reported in individual dogs who've recently swam in cold water (it's also sometimes called «swimmer's tail» or «cold tail.») (animals.howstuffworks.com)
This condition is known by many names among veterinarians, such as limp tail, dead tail, limber tail, sprained tail, swimmer's tail, cold tail, sprung tail, and broken tail. (thesprucepets.com)
Some of the health problems that most commonly affect the Labrador Retriever and Corgi include eye ailments, joint dysplasia, ear infections, skin issues, bloat, epilepsy, cold tail, osteochondritis dissecans, back problems, obesity, and intervertebral disk disease. (petguide.com)