ChatGPT follows the naming convention established by InstructGPT and WebGPT -- it's a model fine-tuned on human preferences for good chat outcomes. The name doesn't roll off the tongue, but then, neither does "Airbnb" and that's a verb now :)

By their own admission they were quite surprised ChatGPT caught on as much as it did; I don't think they were expecting it to be a huge consumer product as much as a modest "research preview", hence the researchy name.