Cynicism
Etymology
From Greek "kynikos" (dog-like), the nickname of the Cynic philosophers led by Diogenes, who lived with pointed simplicity and shameless candor — perhaps from their "dog-like" austerity, or the Cynosarges gymnasium in Athens. The austere philosophy lent its name, over time, to sneering distrust.
noun · /SIN-i-siz-um/
A distrustful belief that people are motivated purely by self-interest.
What it names
The reflex of assuming the worst of human motives — often mistaken for insight.
Example
Years in politics had left her with a cynicism that read every kind gesture as a maneuver.
Related idea
Skepticism withholds belief until there is evidence; cynicism has already concluded that motives are base. One is open and inquiring; the other is closed and sure.