In Book XI of Homer's Odyssey, Odysseus travels to the ends of the world and conjures up the spirits of the dead. Some translators of this book choose to render the Greek word psyche as "shade", rather than "ghost" or "spirit."
I think that our English word "shade" is related to the word "shadow", and so perhaps we can think of the dead as "shadows" of their former selves (literally). Interestingly, our English words "shade" and "shadow" may ultimately be derived from the Greek word skotos, which can mean "darkness."
I would point out that neither Autenreith's dictionary of Homer Greek nor Liddell and Scott's Greek Dictionary offer "shade" as a definition for psyche. Thus, it would imagine that some translators of Homer like the word "shade" because they regard it as more poetic sounding than "ghost" (which seems like a rather mundane word; cf. Casper the Friendly Ghost) or "spirit" (which carries a religious connotation for many English speakers; cf. Holy Spirit).