means A space of time or distance between two points, events, or things.

from From Latin intervallum, literally the space "between the ramparts" (inter, "between," plus vallum, "rampart" or palisade). A vallum was the wall of stakes a Roman camp threw up for defense; the intervallum was the gap between that outer wall and the troops inside — a deliberate empty zone. The word marched into English through Old French in the medieval period, shedding its soldiers and keeping only the gap.