Even a nodding acquaintance with classical Greek will tell us that a chronogram is writing that’s connected with time. Etymology will not take us any further and we have to consult the reference books for additional enlightenment.
A chronogram is a phrase or sentence, often an inscription, in which certain letters, taken to be Roman numerals, express a date. The letters available are I, V, X, L, C, D and M, though we moderns are allowed to cheat with three not in the Latin alphabet: J can be taken to be I, U to be the same as V and W to be a double U or VV. A famous example appeared in an old pamphlet, attributed to George Wither: “LorD haVe MerCIe Vpon Vs”. If we add the Roman numerals up, we get 1666, the date of publication.
Such encoded dates were once popular, especially on medals and on bells to show the date they were cast. In the latter part of the nineteenth century, James Hilton wrote three big books detailing every example of the technique he could find. The arrival of the first of these prompted this verbal assault:
It is impossible to think of any more witless, pointless effort of literary ingenuity. ... We confess to a feeling of dread lest the thing should spread and become common. Nothing can be more likely unless it is nipped in the bud. We have hardly yet got rid of ‘double acrostics’. They linger still in the back pages of some of the ‘society papers’. But chronograms are so much more foolish, so much more senseless, and so much easier to make and to guess, that there is every reason to fear an outbreak of them before long.
Saturday Review, 6 Jan. 1883. Quoted in The Oxford Guide to Word Games, by Tony Augarde.
Isaac D’Israeli (father of Benjamin Disraeli) didn’t think much of chronograms either, describing them as “literary follies”. In 1888, the Birmingham Daily Post greeted the publication of the second of Mr Hilton’s volumes by calling them “vexatious and gratuitous fritterings”. Whether it was the force of these criticisms, or the narrow compass offered by the technique, they fell out of favour.