dinner

Dinner comes from Middle English dyner, from Old French disner, which originally meant "breakfast" (later shifting to "lunch"). This traces back to Vulgar Latin *disiūnāre, from Latin dis- plus iēiūnō, "to break the fast."

The word started out naming the meal that ended a night's fasting, but as it passed through Old French it came to mean "lunch," and in English it eventually settled on the main meal of the day, whenever that happened to fall.

The French descendant dîner shows the same root still living on, carrying the "breaking the fast" idea forward into modern French.