the.com/ripple tank

means A shallow glass tray of water used in physics classrooms to demonstrate wave behavior — reflection, refraction, diffraction, interference — by lighting it from above or below so the wave patterns cast visible shadows on a screen.

from A straightforward compound of 'ripple' (a small wave, from Middle English, origin itself uncertain) and 'tank' (a large container for liquid, which English picked up around the 1600s from Gujarati/Marathi 'tanka' or possibly Portuguese 'tanque', a reservoir). The device itself is a 20th-century teaching invention — physics educators needed a way to make waves literally visible, so they put water in a tray, shone light through it, and let the shadows do the explaining. No myth to debunk here; the name just does exactly what it says.