Portable Digital Player. It is of course obvious that music into an MP3 player is a one way trip. 
Spotlight on:
At this historic milestone, we want to thank music lovers everywhere for making iPod such an incredible success said Steve Jobs
Source: http://news.digitaltrends.com/article12643.html
In some other things of interest, such as getting things for free, here is a way to potentially get a free MP3 Player you might not have thought about. Will have more on ipod case airplane later.