Origins
Behind every tragedy stands a goat. The word tragic comes from Greek tragikós, from tragōidía — a compound of trágos ('goat') and ōidḗ ('song'). A tragedy was, at its root, a goat-song.
Why a goat? The ancient sources disagree. Some say a goat was sacrificed to Dionysus at the beginning of dramatic festivals. Others claim a goat was the prize awarded to the winning playwright. A third theory holds that early performers dressed in goatskins to represent satyrs, the goat-like companions of Dionysus.
What is certain is that Greek tragedy grew from religious ritual. The City Dionysia, Athens's great dramatic festival, was a sacred event. Aeschylus, Sophocles, and Euripides wrote not for entertainment but for worship. Their plays explored the most painful questions — fate, justice, the cost of pride — under the protection of the god of wine and ecstasy.
Latin Roots
The word reached English in the 16th century via Latin tragicus. By then its religious origins were invisible, and tragedy meant simply a drama with an unhappy ending. The further weakening — 'a tragic waste of talent', 'tragically bad weather' — belongs to modern English.
Aristotle defined tragedy as an imitation of a serious action that arouses pity and fear, producing catharsis. The goat disappeared from the definition. But it never left the word.