Greek sarx means flesh; sarkazein, the root verb, meant to strip or tear flesh, used of dogs and of hoofed animals tearing grass, before it meant to sneer. Aristophanes uses it of starving Megarians gnawing like curs; the sneering sense is post-classical. Latin sarcasmos carried the mockery into late antiquity; English took it in the 1570s as sarcasmus, a biting taunt. Its cousin sarcophagus, flesh-eater, named the limestone that decomposed bodies quickly.
The etymology preserves what speakers forget: sarcasm is aggression wearing irony's permit. The Greeks heard the dog in it. Oscar Wilde called it the lowest form of wit and the highest form of intelligence in the same sentence, which is itself sarkazein, tearing the thing while praising it.
The claim: sarcasm is the only socially sanctioned form of verbal mutilation, the bite that cannot be prosecuted because the wound is deniable; its etymology confesses what its users conceal, that the target is flesh and the intent is tearing. Verdict: the root supports it and every schoolyard confirms it, but irony also does work teeth cannot, saying the unsayable at oblique angles. Same mouth. Different meal.
What does it say about wit that its root verb describes what dogs do to carcasses?