The word "until" is a preposition and a conjunction used to indicate a point in time when an event will occur or when a condition will be fulfilled. Essentially, it denotes a limit or endpoint in time, suggesting that something will happen or continue to happen up to a specified moment.
The word "until" originates from the Old English "untill," which is a combination of "un-" (meaning "not") and "til" (which is related to "to" or "toward"). Over time, it evolved into its current form in Middle English before solidifying as "until" in Modern English.