The word "since" is used to indicate a specific point in time when an event or action began and continues up to the present or up to another point in time. It can also be used in reasoning to show causation or a reason why something has happened.
The word "since" originates from Middle English "sithens," which means "from that time." It is derived from Old English "sithen," meaning "after that" or "afterwards." The root can be traced back to the Proto-Germanic "*sithiz," which is related to the concept of time and sequences.