The word "yt" appears to be a typo or an abbreviation. It might refer to "yet," an adverb used to indicate that something has not happened up to a specified time. Assuming you meant "yet," it signifies something that is still pending or has not occurred, often used in negative or interrogative sentences.
The word "yet" originated from the Old English "giet," which means "at this time" or "still." Over time, it evolved through Middle English into its current form.