At this point I don’t know where else to look, so I agree with @Robert that using a word now might not be a bad idea. I will keep researching Cagliostro, although I have already been through his life story a few times and I am not quite sure what in there would be used as a password. I have moved to the serpent type design on The Cagliostro’s mainpage. There are a few serpent references in relation to Cagliostro, one being his seal( as pointed out by @Leigha above), but there is also Ouroboros, the serpent biting its own tail. It originated in Egypt and is often used as a symbol pertaining to alchemy and other aspects pertaining to alchemy and I guess Cagliostro drew that symbol when asked for his “secret sign”.
The link to the Wikipedia page for Ouroboros is here: