Sneaker feels like a really natural thing for me to say, but the term is mostly relegated to the northeastern United States and parts of Florida. Almost everywhere else calls them tennis shoes, except in Chicago and Cincinnati, where a majority of people say gym shoes. Those words sort of make sense, but why do we call them sneakers? The earliest recorded usages were from New England back in the late 1800s, shortly after the shoe was invented. The name referred to how the rubber soles made much less noise than leather shoes, and thus the wearer could sneak around in them. Even earlier, the word sneak was used to mean "quiet shoe", so that may have influenced things, as well. The verb sneak could be from Middle English sniken, meaning "crawl", but it's hard to know for sure. There may be a relation to the word snake.
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.