UPDATE: Woody (Duane), one of the coolest kids in the world, created the name, and helped popularize it. Someone currently unknown put it in Urban Dictionary.
Urban Dictionary defines it as:
An slang explanation used in certain internet circles to denote that a homerun has been hit by Philadelphia Phillies first baseman (2005 Rookie of the Year) Ryan Howard.
“Howard just went deep! Popozao!”
Popozao means a multitude of things, and was famously brought to the United States by the legendary Kevin Federline in the song Popozao (watch the video). But the best definition of popozao is a Ryan Howard home run. It’s all that can be said of what are usually mammoth blasts into the outfield stands. Whether they are to left, center or right, he sprays them to all fields, and does it with AUTHORITY. His slam in last night’s 9-6 victory over Atlanta traveled deep into the right field stands. 39 home runs have been hit by Howard, with many more likely to come. It’s extremely probable that he passes 50 in only his second season. The man has also added patience to his power, and been sporting an impressive 294 batting average, which many doubted he could reach because of a high strikeout rate. He is utterly intimidating at the plate, as his presence has started to force the opposition to simply pitch around him, and still fail. Howard’s at bats have become events. Events that increasingly end in a positive way for the Phillies.
Indeed, the only way to describe the home run shots he hits is POPOZAO!!!!!!!