It is imagined that when a husband and wife have a terrible fight, the wife might throw the husband out of the house, and having nowhere else to live, he will wind up in his backyard, living with the pet dog in the doghouse. This rather colorful situation probably does not ever actually happen (or if it has happened, is extremely rare) but people find it to be a useful metaphor for being in a state of extreme disfavor.
He was behind on what their doing know
In trouble. The image is of your spouse kicking you out of the house and you have to spend the night with the dog.
He was behind on what their doing know
"To be" is not an idiom - it's a verb.
If you are in the doghouse, you are in trouble with your spouse and/or family - imagine a husband whose wife is so mad that she locks him out of the house and he has to spend the night in the doghouse with the family dog.
Pest is not an idiom. It's a word.
The idiom "apple shiner" means the teacher's pet.
The meaning of the idiom in the pink of health means being in good health.
It's not an idiom - to cope means to deal with, or to handle
The idiom means impress someone is egg on
"Old hand" is an idiom meaning having lots of experience.
It is not an idiom. It is an expression. The difference is that an idiom's meaning cannot be derived from the meaning of its individual words. In the expression wolfing down food, the meaning is clearly derived from the meaning of the words, and people have been saying it for hundreds of years.