What is "epipsychidion"

Epipsychidion is a major poetical work published in 1821 by Percy Bysshe Shelley. The work was subtitled: "Verses addressed to the noble and unfortunate Lady, Emilia V--, now imprisoned in the convent of --." The title is Greek for “concerning or about a little soul" from epi, "around", and psychidion, "little soul".