As until recently it happened with the SMS (which developed an almost shorthand language, type "ola k ase"), or as is currently the case with the zip, the arj or the rar, send messages in the past, before the Internet existed It was also expensive so that brought a whole tradition of message compression.
One of the main investors or promoters of this message condensation culture, adapted to the time when people communicated through the Morse electromagnetic telegraph, was the congressman Maine Francis O. J. Simith with your manual: The Secret Corresponding Vocabulary; adapted for use to Morse's Electro-Magnetic Telegraph: and also in conducting griten correspondence, transmitted by the mails or otherwise ("Secret correspondence vocabulary; adapted for use in the Morse electromagnetic telegraph; and also for handwritten correspondence, sent by mail or other means").
As he explains James Gleick in Information:
It was just a numbered alphabetical list of fifty-six thousand English words, from Aaronic to zygodactylous, plus the corresponding instructions. "We assume that the person who writes and who receives the message are in possession of a copy of this work," said Smith. "Instead of sending their communiqués in words, they send only numbers, or one part in numbers and another in words."
Actually, the first objective of this kind of manuals was to encrypt messages, so that outside eyes could not snoop into the content.
But Smith's work, like many other brochures and manuals of the style, such as that of E. Erskine Scott Three Letter Code for Condensed Telegraphic and Inscrutably Secret Messages and Correspondece, facilitated a way of understanding the messages, and consequently a way that they would be cheaper or transmitted faster.
Abbreviating messages meant saving money. The clients thought that the mere substitution of words by numbers served very little in this regard: it was difficult to send a message with “3747” than with “pyrite”. Thus, code books became phrase dictionaries. Its purpose was more or less to put the messages in capsules, impenetrable to nosy looks and suitable for effective transmission. And naturally, from the point of view of the recipient, to get them out of them.
The message encryption and condensation manuals they no longer only contained words but geographical names, names of people, publicly traded companies, and even shipping records.
In the next installment of this article, we will see some of these manuals in depth.