What is the origin of the word 'casserole'?
The word casserole has been in French since at least 1583, meaning one type of dish for cooking in.
The word came into English from French in or before 1706, with the same sense.
Since at least 1958 "casserole" in English has also referred to the food prepared in the utensil itself.
Since 1930 or earlier, "casserole" has also been used
(i) as a verb, meaning "to cook in a casserole (utensil)"
(ii) figuratively, to mean a blend of some kind