means A moving disturbance that travels through a medium or space, carrying energy from one place to another — whether in water, sound, light, or a friendly hand raised in greeting.

from From Old English 'wafian,' to wave the hands, and the related 'wæfre,' restless or wavering — kin to a whole Germanic family of words for unsteady, fluttering motion. The watery 'wave' came later, when the older English word 'waw' for a swell of the sea was reshaped by this verb of fluttering. So before the sea, there was the trembling hand; the ocean borrowed its name from the gesture.