So Dr. Johnson observed in his Preface to A Dictionary of the English Language in 1755; now a team of physicists and economists have published a study of the statistical patterns governing this growth cycle, based on the corpus of GoogleBooks. They examine the life cycles of words in English, Spanish and Hebrew. I did try to read the article, which is available in Scientific Reports, but it was way over my head. The graphs are a bit easier to follow. And here's a link to an article for us lay-folk, in the Wall Street Journal. Reporter Christopher Shea comments:
The authors even identified a universal "tipping point" in the life cycle of new words: Roughly 30 to 50 years after their birth, they either enter the long-term lexicon or tumble off a cliff into disuse. The authors suggest that this may be because that stretch of decades marks the point when dictionary makers approve or disapprove new candidates for inclusion. Or perhaps it's generational turnover: Children accept or reject their parents' coinages.