The Vietnamese word "ẳng" is primarily used to describe the sound that a dog makes when it yelps. It is often used in contexts where an animal, especially a dog, expresses pain or discomfort.
Con chó bị đánh ẳng lên mấy tiếng
(The beaten dog yelped several times.)
Chó con ẳng ẳng khi nó bị mất mẹ.
(The puppy yelped when it lost its mother.)
In summary, "ẳng" is a descriptive word used for the yelping sound made by dogs, especially when they are in pain or scared.