Secret Language, by Barry J Blake

Wordplay with hidden delights

Julius Caesar wrote in code. It wasn't that he wrote in Latin (baffling enough in itself, as I recall) but he concealed his meaning in private messages by jotting down the letter three along in the alphabet from the one he had in mind. To be accurate, Caesar used a cipher: he substituted one letter for another. A code uses entire words to deceive, as in "This is White Rabbit calling" (unless you actually possess a white snout and whiskers).

The beginning and end of Secret Language stray beyond the title's terrain into palindrome and parody, which do not seek to deceive. Otherwise, Barry Blake gives us an enthralling survey of things that signify other things. No sooner did people learn how to express themselves, he declares, than they began to work out how to stop outsiders from knowing what they were on about.

One method was "steganography": concealing the fact there is a message at all. A Royalist prisoner in Colchester Castle received a long-winded message from a friend: an acrostic with the first letter of each line spelling out, "Panel at east end of chapel slides."

An all-round Renaissance genius came up with an all-round Renaissance device of two interlocking, concentric discs, each with letters of the alphabet round their rim. To encipher a letter you wrote down its "partner" on the other disc, giving the occasional twirl to create new partners. Although possessing infinitely greater complexity, the German Enigma machine in the Second World War used roughly the same principle.

No technology at all is required by secret languages such as Polari, a combination of Italian, Yiddish and coded English used by gays when "blue" (homosexual) activities were illegal. Polari featured in the mid-Sixties radio series Round the Horne but the BBC hierarchy was too straight to notice. Less comprehensible, Pig Latin shifts the first consonant to the end of the word and adds "ay": thus "pig" equals "Igpay" and "Latin" "Atinlay". It is not porky and, not being Latinate, was not used by Julius Caesar.

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