The word "never" is an adverb used to indicate that something does not happen at any time or under any circumstances. It expresses a complete absence or lack of occurrence of an action or event. For example, if you say "I never eat broccoli," it means that you do not eat broccoli at all, not even once.
The word "never" comes from the Old English "nǣfre," which is a combination of "nǣ," meaning "not," and "æfre," meaning "ever." This shows that it originally meant "not ever."