A stew is two or more different foods simmered together in a liquid. The oldest cookbook ever found, the "Apicius de re Coquinaria", contains stew recipes, although these are fish and lamb stews rather than chicken stews. The identity of the author is unknown although there were three Romans with that name between 1 BC and 2 AD and the book is believed to date from that era.
You can actually go back even further because primitive tribes used to boil foods together, which is what a stew essentially is. Archeological evidence points to this type of cookery going back seven or eight thousand years. The invention of pottery, about ten thousand years ago, made cooking stews easier.
Fowl such as chicken has been domesticated for thousands of years and chicken stew has been a longstanding popular dish.
Indians, however, had their own version of stew with lots and lots of onions fried and used as base for the dish. A hearty Indian spiced chicken stew is made in a spicy tomato and cream sauce. Perfect served with yogurt and naan bread.