Hormesis
Etymology
From Greek "hormēsis" (rapid motion, an urging on), from "hormaein" (to set in motion or excite) — the same root family that gives us "hormone." It is a term of toxicology and biology for the dose-response curve in which a little of something helps and a lot harms.
noun · /hor-MEE-sis/
A beneficial biological response to low doses of a stressor that would be harmful at high doses.
What it names
A powerful "mental tool" for reasoning about stress and toxins: it captures why small, survivable challenges — exercise, fasting, cold, even mild poisons — can strengthen a system that larger doses would wreck.
Example
The theory behind cold plunges is hormesis — a brief, controlled shock that nudges the body to adapt and grow more resilient.
Related idea
A biological instance of antifragility (already here): antifragility is the general principle that some systems gain from disorder, while hormesis is the specific physiological dose-response behind it.