Cuil may be "an old Irish word for knowledge", but those of us who learned the language more recently (like, say, in the 20th century) will recognise it as meaning "rear". I've even found a dictionary which indicates that this meaning comes from old Irish. In fact, the only references I can find to it meaning "knowledge" are the word-for-word press release reprints from Cuil themselves.
Ah, but there's a catch. In one of the longer articles, the name is revealed to be "derived from a character named Finn McCuill in Celtic folklore" which is an entirely different thing. In this instance, Cuill is a misspelling of Cumhaill, and the name means, simply, "Fionn, son of Cumhall" (Irish tends to insert and remove the occasional vowel to keep you on your toes), which has this new search engine potentially named after... a female slave. Or maybe "keeping", which might make for an easier backstory for a search engine? In any case, I suspect I'll be continuing to use Google despite this "Cuil" new site (their intended pun, not mine).