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.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.