Having just read Branny's hypnotic thread, I have a question: how come Morpheus isn't related to Orpheus?

how come Morpheus isn't related to Orpheus?

They do rhyme, but they're two different names. It might be related to ορφνη (orphnē) 'darkness; netherworld' which in turn may be related to ορφανος (orphanos) 'orphan'.