The spelling of the French phrase "tour de maitre" can be explained using the International Phonetic Alphabet (IPA). The word "tour" is pronounced as [tuʁ], with a silent final "r" and a nasalized "u." "De" is pronounced as [də], with a close-mid unrounded vowel sound. Finally, "maitre" is pronounced as [mɛtʁ], with a nasalized "e" and a silent final "e." The phrase translates to "master's tower" in English, referring to a tower in medieval castles used by the lord or master of the castle.
An old and spectacular method of passing a catheter or sound through the male urethra; the instrument was introduced with concavity downward and stem parallel with the thighs, then, when the beak was in the neighborhood of the membraneous urethra, the catheter was turned rapidly with concavity upward and the tip swept into the bladder.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.