Roman holiday n.

"occasion on which entertainment or profit is derived from injury or death of another," 1860, originally in reference to holidays for gladiatorial combat; the expression seems to be entirely traceable to an oft-quoted passage on a dying barbarian gladiator from the fourth canto (1818) of Byron's "Childe Harold's Pilgrimage":

But where his rude hut by the Danube lay

There were his young barbarians all at play,

There was their Dacian mother. He, their sire,

Butcher'd to make a Roman holiday!