The story
From tea + light, since they are sometimes used to keep a teapot warm. Compare Dutch theelicht (“tealight”), German Teelicht (“tealight”).
Etymology from Wiktionary, CC BY-SA 4.0.
tealight
Today it means: A small, typically circular candle encased in a thin metal cup, so that it liquefies completely when lit and burns as a wick immersed in molten wax. Full definition →