The term 'Pastoral Plaint' is a poetic form of writing that originated in the Middle Ages. It is characterized by its use of rural imagery and themes, often focusing on the beauty of nature and the joys of pastoral life. The crossword solution for this term is BAAS, which stands for 'Bucolic Aesthetic and Acoustic Sensibility'. This term refers to the aesthetic and acoustic qualities of pastoral poetry, which are often described as being peaceful, calming, and tranquil.