The word pony was first attested in a 1659 Scottish diary as powny. Thereafter, it underwent some variation, taking on forms like ponie, powney, pownie, and poney before becoming standardized by 1900. All of it comes from French poulenet and Old French poulain, with the same definitions. However, as Latin pullanus, the word could refer to the young of any type of animal. Pullus, the earlier version of that, meant the same thing (and is also the etymon of pusillanimous and the game of pool, I'll have to explain those later), and it all derives from the reconstructed Proto-Indo-European root pelh, also with the same definition. Pony peaked in usage at the turn of the twentieth century and has recently experienced a bit of a resurgence in utilization in literature over time.
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.