I have heard of this word as cited to contain the most i’s of all English words. I had never heard of it before, but when I copied and pasted it into my email program, lo and behold, the picky spellchecker didn’t bat an eyelid!
Has anyone ever seriously used this word, or any other word of comparable length? How in the world did my spellchecker know about a word nobody will ever use?
Your spellchecker didn’t bat an eyelid because it is simply comparing that word to a list of known properly-spelled words. Despite there being about a quarter-million words in the English language, plus about another 50,000 proper nouns which are commonly included in spelling dictionaries and about another 50,000 “common” technical terms, when properly sorted and indexed it is trivial for a computer to perform a check of each word against this list in real time. On the flip side of that coin, the spell-checker feature of whatever application you use would take a severe credibility hit if the user entered a known good word that the dictionary didn’t know about and marked as incorrectly spelled. So, to be on the safe side, the spell checker developers included a dictionary of every word and term, however unlikely the user is to ever type that word.