pia

The word stems from medieval Latin. The literal translation is “tender mother” and appears in the Salve Regina (Hail Queen). O pia, O dulcis Virgo Maria. O clement, O loving, O sweet virgin Mary. The full name of this thin, fibrous membrane is “pia mater.” Mater is Latin for mother. Even though the pia is a barrier that closely covers the brain, it allows blood vessels to pass through and nourish the brain. It also helps in production of cerebrospinal fluid. source - wordgenius