See armil explained here, except that the links are broken, I presume by the relocation of the Board to a new server some months ago which caused the severing of some older threads. Perhaps someone, more savvy than I, can tell you how to retrieve them.

As to etymology, I think it had to do with a long-bygone Hogwash game whose target was "armil" (having to do with armillary spheres or planetaria or some such), at which several people independently presented "armadillo"-like entries in an attempt to seduce the gullible, all with the same red herring.

Am I close?