Why do people like to use "dogs" to make metaphors, such as single dogs, tired into dogs?

Dogs are probably the hardest and most pitiful animals in the world, so someone will use "dogs" to express their tiredness or very embarrassing situation, such as "single dog" and "tired dog". There are many excellent qualities on the dog, such as very loyal to their owners and diligent. As the pets become more, more and more dog breeders have become more and more, and people also like to use dogs to express their feelings in their leisure time, so that others can experience themselves more vividly to experience themselves. Feeling and sympathy and understand your situation.
Single dogs generally refer to those who have many couples around, but they are single. It is actually a kind of jealousy to say that it is a single dog. Envy others have objects but do not. The three words of single dogs generally appear below: the friends around them have taken off the order, and there is one of ourselves. At this time, we will claim to be a single dog. The pink bubbles cause the single family to be extremely uncomfortable. At this time, we will let the other party not sprinkle dog food for single dogs like ourselves.
The so -called "tired dog" means that it is very exhausting when you do a certain labor. Dogs are very active animals. They often like to run around and often look for food on the streets and alleys. Therefore, in the eyes of many people, dogs are very hard animals. And people are also a very hard animal. Sometimes, for their own work, people often run around, nine to five, no day and night. Early, sleeping later than dogs. " And "tired dog" is also describing his hard work.
The nouns like this are actually many, and of course the animals used are not just dogs, but also cattle, cats, sheep, etc. But without exception, these new nouns are because people do something related to the animals in the nouns in doing something.

People like to use dogs as metaphors, this should be a global topic. Tired dogs have a corresponding word in English called DOG-TIRED. It comes from a long -term allusion. It is said that the British King Alfred Emperor asked the two sons Athelbro and Edwin to chase his hunter. Whoever recovered more, who could get supreme honors that night -sitting on his right to eat. The two sons struggled to chase the dog, and when they came back, they were naturally tired than the dog, so they had the word. It can be seen that "tired dog" is originally a very noble thing. I often use ridicule now.

Because the relationship between dogs and people is relatively close, people like to use "dogs" to make metaphors. It may be more kind.