cynicyoudaoicibaDictYouDict[cynic 词源字典]
cynic: [16] Originally, the Cynics were a group of ascetic philosophers in ancient Greece. Their founder, around 400 BC, was Antisthenes, a follower of Socrates. They advocated the view that virtue and self-control are the highest good and, particularly under their later leader Diogenes, came to exhibit a contempt for the frailties of their fellow human beings that is traditionally said to have earned them their name: Greek kúōn meant ‘dog’ (it is related to English hound), and the philosophers were allegedly dubbed kunikós on account of their ‘dog-like’ sneering.

A more prosaic but more likely explanation of the term is that it comes from the Kunósarge, the gymnasium where Antisthenes taught (perhaps later influenced by kúōn). English acquired the word via Latin cynicus.
[cynic etymology, cynic origin, 英语词源]
cynic (n.)youdaoicibaDictYouDict
mid-16c., in reference to the ancient philosophy, from Greek kynikos "a follower of Antisthenes," literally "dog-like," from kyon (genitive kynos) "dog" (see canine). Supposedly from the sneering sarcasm of the philosophers, but more likely from Kynosarge "Gray Dog," name of the gymnasium outside ancient Athens (for the use of those who were not pure Athenians) where the founder, Antisthenes (a pupil of Socrates), taught. Diogenes was the most famous. Popular association even in ancient times was "dog-like" (Lucian has kyniskos "a little cynic," literally "puppy"). Meaning "sneering sarcastic person" is from 1590s.