明後日 (myōgonichi: day after tomorrow)
the coming (day) + after + day
I’ve always thought 明 meant only “bright” or “light,” but I’ve just learned from Jack Halpern’s Kanji Learner’s Dictionary that in the context of 明後日, 明 means “next” or “the coming (day).” Now 明日 (ashita: tomorrow, next + day) makes a lot more sense!