As nouns the difference between dog and pappy

is that dog is a mammal, Canis lupus familiaris, that has been domesticated for thousands of years, of highly variable appearance due to human breeding while pappy is father.

As an acronym DOG

is digital on-screen graphic.

As a verb dog

is to pursue with the intent to catch.

As an adjective pappy is

like pap; soft; mushy.

As a proper noun Pappy is

one's grandfather.