cynic

Concise Oxford English Dictionary © 2008 Oxford University Press:
cynic /ˈsɪnɪk/

▶noun

• 1 a person who believes that people are motivated purely by self-interest.

  ■ a sceptic.

• 2 (Cynic) a member of a school of ancient Greek philosophers characterized by an ostentatious contempt for wealth and pleasure.

– derivatives
cynicism noun.

– origin C16: from L. cynicus, from Gk kunikos; prob. orig. from Kunosarges, the name of a gymnasium where Antisthenes (the founder of the school of philosophy) taught, but popularly taken to mean ‘doglike, churlish’, kuōn, kun-, ‘dog’ becoming a nickname for a Cynic.