Fun fact: the fear of balloons is called globophobia (the root being from Latin globus, meaning "sphere" and the etymon of globe). The word balloon, however, is far more fascinating in its etymology. It was borrowed into English in the 1570s to describe a trendy children's game where an inflated leather ball was kicked back and forth by children- sort of an early soccer, if you will. This evolved to mean a very different kind of inflated sphere over time, obviously. Before that, balloon came (possible through French) from Italian pallone, which simply meant "large ball", which is augmentative of palla, "ball". One way or another, this is thought to derive from the Lombardic palla, which could also mean "bundle", and that would be, through Proto-Germanic ballo, from the Proto-Indo-European reconstruction bhel, meaning "to swell" or "inflate". Usage of the word balloon in the literature only took off in the 1780s when it first came to mean "helium- or hydrogen-filled vessel", and has been increasing sicne then.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.