Words and phrases are fundamental building blocks of language and culture, much as genes and cells are to the biology of life. And words are how we express ideas, so tracing their origin, development and spread is not merely an academic pursuit but a window into a society’s intellectual evolution.Digital technology is changing both how words and ideas are created and proliferate, and how they are studied. Just last month, for example, the Library of Congress said its archive of public Twitter messages has reached 170 billion tweets and rising, by about 500 million tweets a day. The Library of Congress archive, resulting from a deal struck with