Final answer:
The secret Pi Kappa Phi publication is not specified in the reference material and is typically a private document used for internal fraternity purposes containing confidential information related to rituals and traditions.
Step-by-step explanation:
The esoteric (secret) Pi Kappa Phi publication that consists of a combination of three of the founding father's last names is not explicitly mentioned in the provided reference material. However, in general, esoteric publications for fraternal organizations, including those of Pi Kappa Phi, are often for internal use only and contain rituals, historical information, and other details meant to be kept confidential within the fraternity membership.
These types of publications play a role in the initiation processes and the preservation of the traditions and secrets of the organization.