The expression “to tell a cram” arising from the jumble of voices at Burke's is usually attributed to Lenehan, and rightly so, as it is yet another example of the old chestnuts that he is so fond of roasting. Gifford comments rather laboriously:
a cram - Slang for something that fills the mind with false or exaggerated expectations
which obscures the fact that Lenehan borrowed the phrase tell a cram as a whole.
The emergence of the expression (as a noun) occurred as a play on telegram when the newfangled telegraphy took the world by storm, as the following examples show:
... the lying messages brought by the electric wire make it perfectly proper to call the dispatch a Tell-a-cram.
Punch (1857), 24 October, p. 140
Supposed origin of the word telegram. — Tell a cram.
Household Journal (1862), 22 March, p. 397
I am not in the habit of reading the recurrent highly favoured "dishing up" of a criminal's last moments, by what has been maliciously called the "Daily Tell-a-cram" ...
Truth (1882), 4 May, p. 607
As the OED shows, the slang term "cram" - meaning a lie - was not significantly older than the jokey “tell-a-cram”, though the verb to cram is recorded from the late eighteenth century.
The expression was clearly past its heyday when Joyce put it into a notesheet for the Oxen of the Sun episode in 1920.
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