In 1935, George, Thomas, and John Dempster invented a handy-dandy garbage receptacle that was, shall we say, industrial-sized. They called this the Dempster-Dumpster. Eventually, the Dempster part of the eventual trademark was lost to the ages, but dumpster remains in our vocabulary up till today. The word dumpster is a pretty catchy portmanteau of the word dump (obviously) and the last part of the Dempster surname, just to make the company's new product acoustically pleasing. The word dump, which in context most likely took the meaning "where garbage is put", but had many other definitions as well, comes from the verb form of "throwing something down or away" and by this meaning can be traced back to the Old Norse sound dumpa (which meant "thump", and is also probably the etymon of thump itself, a word with many relatives and few ancestors), probably of imitative or onomatopoeic origin. Dumpster is no longer a trademark (as it expired) and no longer has to be capitalized, so lucky you! You've been unwittingly adhering to copyright law.
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.