What are "George-o-Grams" in the novel, Alternate Side?

George Smythe, a neighbor of the Nolans on the dead-end street, has appointed himself head of various administrative tasks that result in unwanted notes (referred to as "George-o-Grams" (31)) being slipped through the Nolans' mailbox regarding the parking lot, neighborhood parties, the rat infestation, and the like.