I am reading the book Penrod and Sam (1916). There is an episode where the protagonists, 12-years-old American boys, organise a secret society and develop the initiation ritual based on what they know of secret societies; the ritual reflects their limited understanding of the language involved. In particular, their oath sounds "I solemnly swear to keep the secrets in infadelaty and violate and sanctuary". Can anyone comment on it? Does infadelaty mean infidelity? Is it just a random combination of words or is it based on some known oath?