Greek panikos means pertaining to Pan. The Arcadian goat-god dwelt in wild places and was blamed for every unexplained startle: flocks bolting, hunts ruined, strange cries in the mountains. Greek military tradition credited his shout with routing the Persians at Marathon, and armies feared panikos deos, panic fear, as a weapon that moved through ranks without a visible cause. The word entered English through French in the 1600s, already meaning contagious, groundless fright.
Pan's trick was never the roar but the rustle: the wilderness noise that arrives without a source. Greeks propitiated him in caves precisely because his fear came from not knowing where he was. Midday, when the heat stilled the countryside, was his hour, and shepherds dared not nap. The myth maps a real phenomenon: unexplained sound in empty places produces group behavior no commander can countermand.
The claim: the word survives because the phenomenon still lacks a mechanism, stampedes, market crashes, mass fleeing, events where the crowd knows something the individual does not, and panikos is the fossil of our oldest admission that collective fear has an author we cannot see. Verdict: panics are real and their triggers remain hard to model, which is why the word persists. But the god is gone and the markets still stampede; the explanation changed, the physics did not.
If fear once needed a god to explain it, what explains it now that the god is retired?