During the Time of the Judges when there was a famine, an Israelite family from Bethlehem emigrated to the nearby country of Moab - wikipedia 
The book describes how Ruth and a female friend returned to Bethlehem at the beginning of the barley harvest, and in order to support her mother-in-law, Ruth went to the fields to glean. Gleaners are a tradition therefore going back a long way.
As it happened, the field she went to belonged to a man named Boaz, who was kind to her because he had heard of her loyalty to her mother-in-law. Ruth told Naomi of Boaz's kindness, and she gleaned in his field through the remainder of barley and wheat harvest.