湧く
わく · waku · JLPT N3 · verb-godan
to boil
♨️ waku sounds like wok: a wok on the stove boils and grows hot
湧 = 氵 water + 勇 courage: water bravely rising up. 湧く mostly means to gush or spring up, as in 温泉が湧く, a hot spring wells up. For boiling water, Japanese usually writes the same word わく as 沸く.