Herbivore comes from New Latin Herbivora, a group name based on herbivorus. The adjective joins Latin herba to the eating ending -vorus. Its deeper verb is vorare, to devour.
The New Latin group name is part of the word’s history, not a claim that every modern herbivore belongs to one mammal group.
Sources
- Merriam-Webster: herbivore
The noun comes from New Latin Herbivora, a group of mammals, from the neuter plural of herbivorus.
- Merriam-Webster: herbivorous
New Latin herbivorus combines Latin herba, grass, with -vorus.
- Merriam-Webster: -vorous
Latin -vorus comes from vorare, to devour.
- Online Etymology Dictionary: herb
Also built on *herba*: herb (from Latin herba "grass, an herb") and herbicide
- Collins Dictionaries · herbivore
Meanings of the older forms on the word path.