Arcady, or Arcadia, is a Greek region in the located in Peloponnese. It is a relevant location in Greek mythology, as it was the home of Hermes and Pan, two Greek gods (Wikipedia). It is known to be a place full of well-loved nature and revered landscapes, as it is full of vast plains, plateaus, and a river and its tributaries (Britannica). In older European literature and art, Arcadia was considered to be a place of immensely pure and beautiful wilderness, isolated and untainted by external forces (Britannica). Thus, it is often used to convey a sense of purity and wholesomeness.
Arcadia is mentioned once in Beachy Head: "Scenes all unlike the poet's fabling dreams/Describing Arcady" (212-213).
Sources: https://en.wikipedia.org/wiki/Arcadia_(region) , https://www.britannica.com/place/Arcadia-region-Greece