Omnivore is a combination of words taken from the Latin, omne and vorera if the two words are combined then has a meaning to devour. And if interpreted in detail then it has a meaning that is a species that has a different diet consisting of animal and plant.
Although we have often heard of diet like this, but not all animal species that have this diet. Some other animals can only eat meat or we call it carnivores, and there are species that eat only plants called herbivores.