Placate
Etymology
From Latin "placare" (to soothe, to appease), closely related to "placere" (to please) — the same family as "placid" and "complacent." The shared root points to pleasing or quieting, and English adopted "placate" in the seventeenth century specifically for calming someone who is upset or angry.
verb · /PLAY-kayt/
To calm the anger or hostility of someone; to soothe.
What it names
Useful when the goal is to defuse someone’s anger itself — to bring them down from a boil, whether or not you concede anything.
Example
A sincere apology and a refund were enough to placate the furious customer.
Related idea
Appease often implies conceding to demands to buy peace; placate focuses on calming the anger itself, not necessarily on giving ground.