means A back-and-forth oscillation or trembling motion, whether of a guitar string, a phone on a desk, or the molecules carrying sound and heat.

from From Latin 'vibrare,' to shake, brandish, or quiver — the same verb that gave a spear-thrower the sense of a weapon trembling in the hand before flight. English took up 'vibration' in the 17th century, when natural philosophers began describing sound and light as things that shook through the air. The root is possibly related to a wider family of words for quick, darting movement, a cousin to 'wave' in spirit if not in strict descent.