Ferroelectricity isn’t related to iron like you might think, but it gets its name because it’s analogous to ferromagnetism. Ferromagnetic materials like iron are made up of magnetic domains that have north and south poles. If these domains line up, the material itself becomes magnetic. Likewise ferroelectric materials are made of crystals that are electric dipoles, meaning they have a separated positive and negative charge. If these dipoles line up, the material itself will have a positive and negative pole.
Usually the dipoles are pointing in random directions, but they can be coerced into uniformity. The same way iron’s domains can line up when exposed to a strong enough external magnetic field, a ferroelectric’s dipoles will line up when exposed to a strong enough electric field. They’ll stay that way when the field is removed, as though they have a memory, and because of that memory when another electric field is applied that can change the dipole’s directions they’ll lag behind orienting to the new field, a phenomenon called hysteresis. In a ferroelectric material the switch doesn’t happen all together like it ideally should, different parts of it change direction at different times. Figuring out exactly why took more than 80 years of searching.
In 1935 a german researcher mathematically described ferroic materials as small independent parts called hysterons. Each hysteron would change it’s polarization at a well defined speed when exposed to a strong enough field, but each hysteron could also have a different critical field than its neighbors. Meaning a magnetic or electric field that was strong enough to change one hysteron would have no effect on the hysteron next to it.