Why did the writers of Back to the Future call the "flux" in flux capacitor, and what is a "capacitor"?

“Because the car’s stainless steel body improves the flux dispersal generated by the flux capacitor, and this in turn allows the vehicle smooth passage through the space time continuum.”

I found that pretty funny.

But a capacitor is an electrical component that stores electric charge. Not sure what that has to do with time travel :P

Most likely scenario is that Hollywood screenwriters, who know about as much science as your average Creationist (especially if they’re writing sci-fi) just slapped together two vaguely “sciency” sounding words, regardless of what those words might actually mean, for the name.

Flux is the flow rate of energy/particles through a material.
A capacitor stores energy.
So combining the terms ends up with a device that may store/regulate the energy flowing through the material of the car, which I suppose would be a good thing to do to sync the car with the space time continuum to make it possible to travel through it.

You do know that movie “science” doesn’t have to mean anything, right?

Well I figure that the flux capacitor just stores the massive amount of energy needed to travel through time somehow, as for flux, flux is used to remove the oxide layer from stuff when soldering or welding not melting it.

In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks. A simple and ubiquitous concept throughout physics and applied mathematics is the flow of a physical property in space, frequently also with time variation. It is the basis of the field concept in physics and mathematics, with two principal applications: in transport phenomena and surface integrals.

A capacitor stores charge on the surface of two conductors separated by a dielectric. (Think of two metal plates close together)
Capacitance is the amount of charge that can be stored divided by the applied voltage.

Flux is simply a flow of something through an area of something.

“Flux capacitor” is meaningless