Glucagon

Etymology

Coined in the 1920s from "glucose" and the Greek "agein" (to lead, drive) — roughly "the glucose mobilizer." The name captures its job: it drives sugar out of storage and into the blood.

noun · /GLOO-kuh-gon/
The hormone that raises blood sugar by prompting the liver to release stored glucose.
What it names
The body's counterweight to insulin — the hormone that fights low blood sugar — half of a balancing pair most people only half know.
Example
When a diabetic collapses from severe low blood sugar, an injection of glucagon can bring them around by unlocking the liver’s glucose stores.
Related idea
Glucagon raises blood sugar while insulin lowers it — the two hormones work in opposition to keep glucose in a safe band, so diabetes is at heart a failure of this balancing act, not of one hormone alone.