Many people find exhilarate a difficult word to spell. It's easy to forget that silent "h" in there, and is it an "er" or "ar" after the "l"? It may be easier to remember the spelling if you know that exhilarate ultimately derives from the Latin adjective hilarus, meaning "cheerful." (This also explains why the earliest meaning of exhilarate is "to make cheerful.") Exhilarate comes from exhilaratus, the past participle of exhilarare, which is formed by combining ex- and hilarare, a verb that derives from hilarus and means "to cheer or gladden." If hilarus looks familiar, that may be because it's also the source of hilarious and hilarity (as well as hilariously and hilariousness, of course).