An admittedly extremely old entry in the Oxford English Dictionary defines this as “the action of divagating”. Thanks very much. That sends one to the preceding entry, the verb divagate: “to wander about”.
Divagation isn’t particularly rare and may be readily found in writings of the more literate sort:
While the film’s plot progresses, with a few divagations, in a straight line through the decades of Benjamin Button’s life, the backward vector of that biography turns this “Curious Case” into a genuine mystery.
International Herald Tribune, 3 Jan. 2009. This is in a review of The Curious Case of Benjamin Button, in which the eponymous character lives his life backwards.
The meaning becomes clear when we recall that it derives from the Latin verb divagari, in turn from vagari, to wander. In English the wandering has usually been figurative — deviation, digression or straying from the point.
Dinner at nine o’clock, before the big open hearth, with a friendly fire. Much chaffing and pleasant talk about the arrangements for to-morrow. A man to be sent off at daybreak to have two buckboards ready at the landing at seven for the drive to Tadousac. Then a reprehensible quantity of tobacco smoked in the book-room, and the tale of the season’s angling told from the beginning with many embellishments and divagations.
Days off and Other Digressions, by Henry Van Dyke, 1907.