Possibly relevant outside information[]
According to Euro-Latin phonetics, Rinja's name would be pronounced similar to "Rinya" or "Reenyah", in turn similar to the English word "renal", meaning related to the kidneys.
Just as the kidneys retain or filter out, so Rinja has proved to be a filter admitting Agatha into the body of Mechanicsburg. (Also she works in a coffee shop, which means she works with filters and her wares have an effect on people's kidneys.)