The term 'MATER' (Brain Covering) is composed of two crossword solutions, Dura (4 letters) and Pia (3 letters). Dura is the outermost layer of the meninges, which is a protective membrane that covers the brain and spinal cord. Pia is the innermost layer of the meninges and is the closest to the brain and spinal cord. Together, Dura and Pia form the Mater, which is the collective name for the three layers of the meninges.