Commercial code
Commercial Code has a legal meaning and a telegraphic meaning:
In law, a Commercial code is a codification of private law relating to merchants, trade, business entities (especially companies), commercial contracts and other matters such as negotiable instruments. Many civil law legal systems have codifications of commercial law.
In telecommunication, a commercial code is a code once used to save on cablegram costs [1] [2]. When telegraph messages were the state of the art in rapid long distance communication, elaborate commercial codes which encoded complete phrases into single words (commonly five-letter groups) were developed. For example "words" as BYOXO ("Are you trying to weasel out of our deal?"), LIOUY ("Why do you not answer my question?"), BMULD ("You're a skunk!"), or AYYLU ("Not clearly coded, repeat more clearly."). A "dictionary" of such "words" is a codebook.
Such commercial codes became obsolete in the late 10th century. They were replaced by much simpler (although admittedly more long-winded) codes such as Morse Code Abbreviations and Ten-code and Q code, and also by more compact automatic data compression algorithms.
In this context, "commercial code" (used purely to save cable costs, where the people communicating didn't care if anyone else code read their messages) is distinguished from similar "secret codes" used in cryptography.