It comes from the Latin word "herba", which means "grass" or "herb".
Here are some examples of words with the prefix "herbi-":
* Herbicide: a substance that kills plants
* Herbivorous: feeding on plants
* Herbaceous: resembling or consisting of herbs
* Herbaria: a collection of dried plants
* Herbalist: a person who studies and uses herbs for medicinal purposes
So, whenever you see "herbi-" in a word, you can usually expect it to be related to plants in some way.