Pan
Pan was a god of shepherds and flocks. He was the son of Hermes and a nymph. He was born with the legs and horns of a goat, which caused his own mother to spurn him. He prances through the countryside playing his seven-reed pipe in the wild abandoned forest. When he plays his pipe, it sounds like a soft seductive breeze, but when he's angry, it sounds like a howl that could be heard for miles. He fought with the Olympians against the Titans of Kronos. His was known also for his terrifying war cry his name associated with panic and fear.
Pan was popular with the nymphs and had a passionate desire for nymphs, which are young and beautiful female spirits that personify the natural world. They take the form of any and all things and give life to the ground we walk on. He also desired naiads, which were the nymphs of the springs.
Once, Echo ran away from him and lost her voice as a consequence, being condemned only to repeat the words of others. Another fleeing nymph was transformed into a reed, which inspired Pan to invent the shepherd's pipe of bound reeds of varying lengths.
Pan was considered to be the cause of the sudden fear that sometimes comes for no reason, especially in lonely places. That's why it's called panic.