In ancient times, astrologers remembered the starry skies by identifying the position of stars and location by means of mental images - a cluster of stars = constellation. The knowledge was passed down through the ages via Greek writings etc. People use the stars as navigation tools like when sailing or in the desert before the birth of GPS. The constellation of Orion is welknown because it is easily recognised and can be seen throughout the world.
There are many variations of the myth regarding the life and death of Orion the Hunter but they all agree that upon his death, a request was made by the other gods and goddesses to the Chief God, Zeus, that he be immortalised, depicted as a group of stars in the night skies and thus be remembered by all who gazed up above.