tragedy (n.) late 14c., “play or other serious literary work with an unhappy ending,” from Old French tragedie (14c.), from Latin tragedia “a tragedy,” from Greek tragodia “a dramatic poem or play in formal language and having an unhappy resolution,” apparently literally “goat song,” from tragos “goat” + oide “song.” The connection may be via satyric drama, from which tragedy later developed, in which actors or singers were dressed in goatskins to represent satyrs. But many other theories have been made (including “singer who competes for a goat as a prize”), and even the “goat” connection is at times questioned. Meaning “any unhappy event, disaster” is from c.1500. – from the Online Etymology Dictionary
‘Tragedy’ originated in Greek theatre as the enactment of unhappy events which provoked audience ‘catharsis’ – literally, ‘cleansing’, ‘purgation’ – the ability to rid ourselves of pity or fear through witnessing the sufferings of others – a concept originating in Aristotle’s Poetics. In a classical sense it’s used to define creative empathy.
I am increasingly averse to the overuse of the word ‘tragedy’ in contemporary media, who apply it to everything from the accidental to the criminal – although I’m well aware that it has been used in this sense since the sixteenth century, when it became more generally applied to any events disastrous or fatal.
All sad endings are not, however, ‘tragedies’ in the classical sense – to release responsibility for the preventable to some sense of fatalistic human failing seems to me childish and dangerous in our confused and confusing world.