The words stepfather, stepmother, and stepchild have been around since early Old English, as steopfæder, steopmodor, and steopcild, respectively. I always assumed that the steop part just meant that the person was a step removed from being an actual parent, but it actually meant "loss"! The idea was that you would only get a step-family if you lost a family member; for a while, steopcild was basically a synonym for orphan. Finally, through Proto-Germanic steupa, steop comes from the Proto-Indo-European root steu, meaning "to push" or "hit". In recent years, there has been a push against use of the word step-family, because of pejorative connotations arising from the "evil step-parent" archetype. The movement has adopted the terms bonusfamily or blended family instead, which is a much more positive way of looking at it.
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.