AJAX took the Web by storm and quickly became a buzzword of the day. On almost all sites that has anything to do with web-oriented development there are discussions about AJAX technology, tutorials on how to use AJAX technology, new libraries that support AJAX technology... But, after discarding all that buzz around AJAX, one can easily see that there is nothing new in this "technology". There were several ways to asynchronously call server without reloading the page long before AJAX appeared. One way was to use a hidden frame as a container for the results returned by the server - I used it 6 years ago. Another way was to utilize for the same purpose an invisible IFRAME (used 3 years ago).
Yes, yes - both of these ways are much less elegant than AJAX, and there are certain things possible with AJAX which were impossible with these old tricks (for example, retrieving some data from another site which supports REST). But still, the basic functionality was the same, and the famous example that started the AJAX craze - Google Suggest - could be easily implemented using any of these methods.
So why the old methods did not get that popularity? One reason is, of course, the timing. AJAX appeared at a very right time, and was popularized by Google itself. But there is another reason - maybe more important. It is very simple: "AJAX" is a catchy word, "technology" is a very important-sounding word. "AJAX technology" - this combination just doomed to success.