E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Gibberish (g hard).
Geber, the Arabian, was by far the greatest alchemist of the eleventh century, and wrote several treatises on the art of making gold in the usual mystical jargon, because the ecclesiastics would have put to death any one who had openly written on the subject. Friar Bacon, in 1282, furnishes a specimen of this gibberish, He is giving the prescription for making gunpowder, and says
Sed tamen salis-petræ
LURU MONE CAP URBE
The second line is merely an anagram of Carbonum pùlvere (pulverised charcoal).