The feature appeared dark and sombre; hence, the party gave the name from Milton's "Il Penseroso" in antithesis to Allegro Valley 14 miles to the south.
Charles Jennens (1700 – 20 November 1773) was an English landowner and patron of the arts, who assembled the text for five of Handel's oratorios: Saul, Israel in Egypt, L'Allegro, il Penseroso ed il Moderato, Messiah, and Belshazzar.