Still Running Off at the Keyboard

AMBIGRAMS

Dan Brown has devoted several pages in his website to the subject.

A Wikipedia review of Brown's novel ANGELS AND DEMONS indicates the ambigram plays a centrol role.

As the link in Brown's ambigram webpages indicates, "Langdon" is the name of the creator of the ambigram used in ANGELS AND DEMONS. Coincidentally "Langdon" is also the name of the main character in the novel and in Brown's subsequent novel, TDVC.

In JEWISH MAGIC AND SUPERSTITION, Joshua Trachtenberg describes them, though he doesn't apply the word:

A familiar characteristic of magic is the injunction to do things in reverse, to walk backward, to put one's clothing on backward, to throw things behind one's back. The same principle applies in incantations, and Talmudic and medieval Jewish charms amply illustrate its operation. Biblical quotations were often recited both forward and backward, mystical names were reversed; sometimes the words were actually written backward as they were to be uttered, so that it requires considerable mental agility not to be taken in by the unnatural rendering. Phrases that are capable of being read alike in either direction were especially highly prized. The purpose was to capitalize the mystery of the bizarre and unfamiliar, and the power that is associated with the ability to reverse the natural order of things. (p. 116)