The word "through" is a preposition that indicates movement from one side to the other of something, like a space or an obstacle. It can also refer to being involved in or experiencing something completely, such as a process or time period.
The word "through" comes from Old English "þurh," which is related to similar words in other Germanic languages. It has been used in English since the early Middle Ages, retaining its fundamental meaning related to the passage or movement within a space.