Panic

In Greek mythology, the god of flocks, fields, and woods is Pan, a man with the legs, horns, and ears of a goat. Pan's name is also cited by the AHD as the ultimate source (in the Greek language) for the word "panic." Panikos, is defined as being "of Pan (a source of terror, as in flocks), groundless (AHD)."

Prior to entering the English language, panic went through French--and picked up some extras as it lingered: panique (terrified)(AHD).

The word is now used to characterize, as defined by AHD (italics mine, to show how 'flock' stuck-around from its origins in Greek, until today):

1. A sudden overpowering terror, affecting many people at once.

2. A sudden widespread alarm concerning finances, often resulting in a rush to sell.

3. Slang One that is uproariously funny.