Origins
The word 'cynic' links one of the most provocative philosophical movements in history to one of the most familiar animals in human experience: the dog. Greek 'Kynikos' (Κυνικός) meant 'dog-like,' from 'kyon' (κύων, genitive 'kynos'), the standard Greek word for dog. The Proto-Indo-European root *ḱwón- (dog) is one of the best-attested words in the proto-language, with reflexes in nearly every branch: Latin 'canis,' Old English 'hund' (hound), Sanskrit 'shvan,' Old Irish 'cú.'
Why a philosophical school should be named after dogs has been debated since antiquity. Three explanations circulate, and all may contain partial truth. First, Antisthenes — the Athenian philosopher who founded the school in the early fourth century BCE — taught at the Cynosarges (Κυνόσαργες), a gymnasium outside the city walls whose name may mean 'white dog' or 'swift dog.' The school may simply have been named after its meeting place, as the Stoics were named after the Stoa.
Second, the Cynics may have embraced the label as a badge of honor. Diogenes of Sinope (c. 404-323 BCE), the most famous Cynic, deliberately lived like a dog: he slept in a large ceramic jar in the marketplace, ate and performed bodily functions in public, barked at people he considered foolish, and rejected every social convention he could identify. When Athenians called him a dog, he reportedly replied that he was indeed a dog — specifically, a hound of the breed that people praise but no one dares to hunt with.
Development
Third, the comparison to dogs may have been originally hostile — an insult from critics — that the Cynics adopted and transformed. Ancient sources report that the name was applied to Diogenes by others who found his behavior shameless and bestial. His genius was to accept the insult and redefine it: a dog is honest, lives according to nature, guards its friends, attacks its enemies, and is indifferent to wealth and social status. These were exactly the virtues the Cynics claimed to practice.
The Cynic philosophy, insofar as it can be systematized (the Cynics were suspicious of systems), held that virtue is the only good, that virtue consists in living according to nature, and that the conventions of civilization — property, modesty, social hierarchy, even hygiene — are obstacles to the natural life. Diogenes is said to have walked through Athens carrying a lantern in daylight, searching for 'an honest man' and finding none. When Alexander the Great visited and asked what he could do for Diogenes, the philosopher supposedly replied: 'Stand out of my sunlight.'
The word entered Latin as 'Cynicus' and passed into various European languages. English borrowed it in the sixteenth century, initially as a capitalized reference to the ancient school. The lowercase generalization — a cynic as someone who suspects ulterior motives behind apparent goodness — developed during the seventeenth and eighteenth centuries. This shift preserved one element of ancient Cynicism (the suspicion of conventional virtue) while discarding others (the commitment to radical simplicity, the philosophical seriousness).
Modern Usage
Modern cynicism has little in common with ancient Cynicism. The ancient Cynics were radical idealists: they rejected social conventions not because they despaired of goodness but because they believed that natural virtue was superior to artificial propriety. Diogenes was not cynical in the modern sense — he did not doubt the existence of virtue. He doubted that it could be found in the wealthy, respectable, conventionally moral citizens of Athens. The modern cynic, by contrast, doubts the existence of genuine virtue altogether.
Oscar Wilde captured the modern meaning perfectly: 'A cynic is a man who knows the price of everything and the value of nothing.' This definition would have baffled Diogenes, who knew the value of everything (nature, honesty, freedom) and the price of nothing (he owned almost nothing and wanted less). The word's journey from 'one who lives with dog-like natural honesty' to 'one who disbelieves in honesty' represents one of the most ironic semantic reversals in the English language.