I've never failed to be mildly amused by the name Waluigi, in all its magnificent lameness...I assumed that after coming up with the character Wario, they just applied the same prefix to Waluigi, with uncomfortable and hilariously contrived and lazy results. "Waluigi" haha. As a character he's just utterly charmless and unappealing as well isn't he; not even in a suitably villainous way, just in a mundane "slightly creepy Slovakian service station worker" kind of way...
However i've recently gleaned that there's more to the name than meets the ear...apparently 'warui' means 'bad' in Japanese as in morally bad...so it's actually a pretty neat play on words...an English equivalent of this perhaps would be an antagonist called "Badam"...or "Stevil" (Steve-il)
Bit of a stretch but Ji means character, so if this was also applied his name would mean "bad character" I reckon. Its a very effective pun, specially as the decision to call Wario Wario was probably a bit more frivolous, just a variation on Mario. So to then come up with something so fitting was a joyous discovery for me