Cynic (noun)
sin-ik
A person who believes that people are motivated purely by self-interest rather than acting for honourable or unselfish reasons.
Mid 16th century (in cynic (sense 2)): from Latin cynicus, from Greek kunikos; probably originally from Kunosarges, the name of a gymnasium where Antisthenes taught, but popularly taken to mean ‘doglike, churlish’, kuōn, kun-, ‘dog’ becoming a nickname for a Cynic.
Example sentences
“Her friends knew what a cynic she was.”