A hydronym (from Greek hydor (ὕδωρ), "water" and onoma (ὄνομα), "name")'s a proper name of a body of water. Hydronymy's the study of hydronyms and of how bodies of water receive their names and how they're transmitted through history. It can apply to rivers, lakes, even oceanic elements. Like most toponyms, as linguistic items, hydronyms are very conservative, with successor peoples often retaining the name given a body of water. For example, Missis… (More on Hydronym)