Using the same site with a different URL, this will give you a different set of 51 nouns each time:
client = new WebClient();
downloadedString = client.DownloadString("http://www.wordgenerator.net/application/p.php?id=nouns&type=50&spaceflag=false");
string[] randomWords = downloadedString.Split(',');
You can consume this API which will be a better idea.
http://randomword.setgetgo.com/
Screen scraping is a bad idea as screens can change breaking your parsing implementation. Consuming a REST API is more reliable as it should be less prone to change.
You can consume the above API like this:
client = new WebClient();
downloadedString = client.DownloadString("http://randomword.setgetgo.com/get.php");
string randomWord = downloadedString;