panic

The adjective was borrowed from Middle French panique, itself from Ancient Greek panikós, "pertaining to Pan," the Greek god of fields and woods. Pan was believed to cause the mysterious sounds that sparked sudden, contagious fear in herds, crowds, or lone travelers in wild places. The noun developed from this adjective, and the verb later developed from the noun.

What began as an adjective describing something "of Pan" came to describe the fear he supposedly inspired, then hardened into a noun for that fear itself, and finally into a verb for feeling or causing it. One late verb sense even shifted toward the opposite of terror — meaning to delight or wow an audience.

Late Middle English panik/panyk, meaning a plant of the genus Panicum (foxtail millet), came from Latin pānicum — a word possibly tied to pānis ("bread") or pānus ("thread wound on a bobbin"). That millet-word is, curiously, a doublet of bannock.