cynic

1. a person who believes that people are motivated purely by self-interest rather than acting for honourable or unselfish reasons.

   some cynics thought that the controversy was all a publicity stunt

2. a member of a school of ancient Greek philosophers founded by Antisthenes, marked by an ostentatious contempt for ease and pleasure. The movement flourished in the 3rd century BC and revived in the 1st century AD.

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.