The word reggae was popularized by a Jamaican band called the "Toots and Maytals", who named a song Do The Reggay. Soon afterwards, reggay changed (as words do) to become reggae and applied to the style of music propagated by the Toots and Maytals. Before that, though, reggay was known as the rega-rega, which meant "a protest" and was applied to music because it was people's way of expressing themselves. Prior to even that, it was raga-raga and meant "tattered clothes" or something similar, and (I couldn't find any research on this, so I'm just guessing) may be etymologically connected because of a correlation between poverty and protests. At this point, you may have noticed that raga-raga looks like a super-Jamaican-English version of the word rag ("tattered cloth"). This in fact is true! Continuing backward, rag had several alterations in Middle and Old English, going through forms like ragge, ragg, and raggig after ultimately deriving from Old Norse rogg, or "tuft". This may be from Proto-Germanic ruhwaz, "rough", with a contested Proto-Indo-European origin. But, hey! You can really say that the etymology of reggae is a real rags-to-riches story!
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.