Macbeth, Act V, scene V - RhymeZone.com
Ran into the International Phonetic Alphabet on Wikipedia - this strikes me as a very interesting concept: a written language with no vocabulary or grammar of its own. Of course, it definitely doesn't 'signify nothing,' since the characters represent phonemes, but the only meaning of the written characters of IPA is the sound of a word in another language, which then secondarily has a conceptual meaning.
(And yes, I know that I've run into this concept every time I've looked at a dictionary, but I hadn't encountered something this detailed before. :-)