E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Perillo is a little stone, a mark by which Julian del Rey, a famous armourer of Toledo and Zaragoza, authenticated the swords of his manufacture. All perillo swords were made of the steel produced from the mines of Mondragon. The swords given by Katharine of Aragon to Henry VIII. on his wedding-day were all Perillo blades.
The most common inscription was, Draw me not without reason, sheathe me not without honour.