A new feature on Google being called the Books Ngram Viewer provides a historical reference to any terms used frequently enough to show on its charts. The books searched go back to the 1500s. About 72 percent of the books included were written in English. For instance, the charts show the term Manufactured Housing started appearing around 1970. The frequency of the term mobile home seems to have peaked around 1980. It’s been on the decline ever since, but is still mentioned more often than manufactured home. The frequency of the term modular housing seems to have peaked around 1970. The data ends at 2008. Oddly the results change depending on whether you capitalize the entry.