It's the podcasting 2 .0 terminology. They encouraged choosing a rate of sats/min to stream. And then if you liked a part more, you'd give a "boost" or a one time extra (now known as a zap) a boostagram is a boost with a comment added. These comments are viewable across all the Bitcoin enabled podcasting apps, and are frequently read on-air. Anyway it's a boost, because it's in addition to the sats/min stream. An extra pow.