Kyrie eleison is the Latin transliteration of the Ancient Greek phrase Κύριε ελέησον, which means "O Lord have mercy". In Modern Greek it is used in a non-ecclesiastical sense as an exclamative similar to the English "oh my God/gosh!", "what on earth!"
I only learned this on Sunday when I was searching for the Greek word for "mercy."
I geek for Greek.
...and cuckoo for cocoa puffs.