Grimoire

grimoire /grim-ˈwär/ noun: a book of instructions in the use of magic, especially summoning demons

Etymology: Old French grammaire, from Ancient Greek grammatikos relating to letters

I can’t help but see the word grim in grimoire’s first syllable; coincidentally, one could make the argument that the use of a grimoire to summon demons indeed would be grim, i.e., “ghastly, repellent or sinister in character.”