A closure in programming is a concept that doesn't really exist in any other field.

There isn't an existing word that describes the concept, because it didn't exist until functional programming came along.

So there are only two options. You invent a brand new word that doesn't already exist. Or you re-purpose an existing word to give it a new meaning in the specific context of functional programming.

Mathematicians have always faced this dilemma, and have usually gone down the route of re-purposing an existing word. Why does "differentiation" mean finding the slope of a curve, for example?