Why an almanac as a terrorist indicator?

��It's not as ��������risible as NPR finds it to be.

1. an almanac would serve well as a key for a book code. For a good example of a book code in use, read Thomas Harris's Red Dragon. Hannibal Lecter and the darkroom serial killer communicated by citing a specific paperback edition of The Joy of Cooking. That's the catch, though: both users must have copies of exactly the same key. DHS didn't mention a specific edition of a specific almanac, nor do we think they'd be so stupid that they would release that information to the public.
   
   
2. Islam keeps the lunar calendar. For widespread underground cells to limit their communication, it would be advisable to coordinate their actions or their infrequent communications in advance with a calendar that they understood more intimately than their intended victims do. A genuine almanac offers a lunar calendar, among many other useful data.
   
   
3. a mathematical construct of both Item (1) and Item (2). Base your cipher on a table of tides or phases of the moon, or know which cipher to use on which date. The exact same edition or even brand of almanac would not be required for the cipher to work.
   

So all you folks who don't understand why DHS is interested in suspicious persons using almanacs, now you do, so you can now stop your tittering and pay serious attention.

My regular readers, all five of them, will tell you I'm no regular defender of nor apologist for DHS. However, their concern about almanacs, and their willingness to mention them in the clear, appear to me to be signs that they are in earnest search for something very specific.

BTW, the word almanac is a cognate from Arabic, isn't it?

Update: OK, perhaps it isn't an Arabic cognate. Of the three definitions cited by dictionary.com, one's etymology led to Greek and possibly further back to Coptic, one said "unknown" and a third offered no etymology at all. So I say "perhaps," and refuse to blink.