Dave Duncan, a série "Um homem da sua palavra". Personagens principais: Rap, Inos. link
Esta revisão GoodReads do primeiro livro explica a premissa de como as palavras funcionam, combinando os detalhes do questionador:
the source of all magic appears to be these words of power. If you know one then you're super-human in some way [...] A second word makes you great at all human endeavors, and super-human feats like forsight and such tend to go with a second word. A third makes you a sorcerer with arcane powers. [...] However, each person who knows a Word shares the power of the Word - so the more people who know the Word the less power you have