Amphibious (adjective) means “full of amph” or “of an amphic nature.” Neither amph nor amphic is a real word. Thus, amphibious is totally meaningless. It would be funny if it weren’t so utterly pointless and if just considering the word and its definition weren’t such a complete waste of time.
It just goes to show, some lexicographers have absolutely nothing better to do with their time than to create nonsense words to befuddle the masses or, at least, those of the masses who can be bothered to look in a dictionary once in a while.
Don’t scold the lexicographers for their frivolous, deceitful ways. Pity them. Or buy them a scotch. They clearly need a good stiff drink—either that or a fun board game to keep them busy. Nah, the scotch. Definitely the scotch.