Nomenclator
A hybrid of substitution alphabet and codebook that ran European diplomacy for four centuries.
From the 1400s to the mid-1800s, courts and embassies enciphered with nomenclators: a substitution alphabet for running text plus a list of code symbols for names, titles and common words. Larger versions added nulls and multiple symbols per letter to frustrate frequency analysis.
It wasn't always enough. Mary, Queen of Scots, trusted hers; Thomas Phelippes broke it in 1586, and the decrypted Babington Plot letters cost her her head the following year. Louis XIV's Great Cipher, built by the Rossignol family with some 600 numbers standing for syllables, held out for two centuries until Étienne Bazeries cracked it in the 1890s.