why is raining cats and dogs means good luck

The phrase "raining cats and dogs" does not actually mean good luck. It is an idiom used to describe heavy rainfall or a downpour. The origin of this phrase is uncertain, but there are a few theories. One theory suggests that the phrase may have originated from old English or Norse mythology, where cats and dogs were associated with storms and bad weather. Another theory suggests that the phrase may have come from the streets of 17th-century England, where heavy rain would wash away dead animals, including cats and dogs, from the gutters and onto the streets. However, it is important to note that this phrase does not have any direct relation to good luck.