The phrase "wast tail" is an old English term that refers to an animal's tail that has been cut off close to the body, leaving only a short stump. The spelling may seem unusual, but it is in fact an example of the historical vowel shift that occurred in the English language. The word "wast" is pronounced /weɪst/, with a long "a" sound, while the word "tail" is pronounced /teɪl/, also with a long "a" sound.