the.com/pact

A promise with teeth — broken handshakes don't make headlines, broken pacts do.

means A formal agreement between two or more parties who bind themselves to do (or not do) something.

from From Latin pactum, 'something agreed,' the past participle of pacisci, 'to covenant or agree.' That root is tangled up with pax — 'peace' — since striking a deal was literally how warring parties made peace stick. The word passed through French before settling into English, and it's a cousin of 'pay,' 'peace,' and 'pact's' legalistic sibling 'pact-um' showing up in diplomatic treaties for centuries.

etymology
from Latin pactum, meaning agreement already made
fiction trope
usually signed in blood or with a demon
suicide pacts
rare, but disproportionately covered by media
diplomacy use
sounds sturdier than treaty, means roughly the same
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