The Vandals were a real Germanic tribe. In the 5th century CE they migrated across western Europe, crossed into North Africa, established a kingdom centred on Carthage, and in 455 CE sacked Rome itself. Their name in Latin was Vandali, almost certainly from a Germanic root meaning "wanderer."
A Reputation Out of Proportion
The 455 sack of Rome was, by the standards of the period, relatively restrained. The Vandal king Genseric had agreed in advance with Pope Leo I to spare the city's inhabitants and major buildings; what he took was movable wealth, including treasures from the temples. Compared to the previous sack of Rome in 410 by the Visigoths, or the later destruction by the Ostrogoths and others, the Vandals were not especially destructive.
Their reputation, however, fixed itself in Western European cultural memory. Roman writers, eager to villainise the people who had finally broken Rome's long siege, painted the Vandals as uniquely savage. The image stuck for over a millennium.
The 1794 Revival
The English word vandal, in its modern sense of "someone who wantonly destroys property," was effectively coined in 1794 by Henri Grégoire, a French bishop and revolutionary. Watching mobs damage churches and statues in revolutionary Paris, he wrote a pamphlet condemning what he called vandalisme — behaviour worthy of the ancient Vandals. The word caught on in French and was rapidly borrowed into English, where it had been used only as a historical proper noun before.
A Tribal Name as Verb
"Vandal" is one of several English words formed from tribal or national names that became insults: Tartar ("a fierce or troublesome person," from the Mongol-related Tatars), barbarian (from Greek barbaroi, "those who do not speak Greek"), philistine (from the biblical Philistines, used since the 18th century to mean an uncultured person). Each retains a fragment of the historical encounter that gave it its loaded modern sense.