Question

How do you name words like how did people name the word CATEGORIES or DOGFOOD.

Answer 1

well some word like dog-food and cat-fish

are named by their looks, feel, or even what they are used for.

Answer 2

Well, they used prefixes, roots, and suffixes. These are all considered word parts and each have a specific meaning. So when you put certain word parts together, you'll get words like Categories and Dogfood that create one word with one meaning. Hope I helped!