Where does “quesadilla” come from?

quesadilla (English) comes from Spanish quesadilla, from Spanish Quesada, from Spanish queso, from Old Spanish queso, from Latin cāseus, from Proto-Indo-European kwat- — to ferment, become sour; to boil.

quesadilla (English): A Mexican dish made by filling a tortilla with cheese and sometimes other ingredients and then cooking it until the cheese is melted