Deux-Epées
Madame les Deux-Epées is the fencing teacher and mistress-at-arms at the Assassins' Guild school. She is young, or relatively young-looking, and that she is probably Quirmian in origin. She is known to spit out the word "swordsmanship" as if the "man" in the middle is a personal insult. She is therefore evidently a Woman of Opinions. She is also house mistress of the all-female Black Widow House.
The Assassins' Guild Diary also adds the information that in the old days, when education at the Guild School was strictly male-only, a few enterprising Polly Perks had enrolled in the then all-male Guild school, by means of a short haircut, a spare pair of socks down the britches, and a note excusing them from gym classes. Madame Deux-Epeés was such a one, whose Guild membership was retrospectively approved so as to avoid embarrassment, who later became House tutor for Black Widow House after the Guild school went co-ed, and now teaches Edged Weaponry and Fencing. She suceeds Mr Wilkinson, who in his turn suceeded Mr Stanley 'Touché' Danpipe after his unfortunate work-related injury.
Her likeness, sketched by Paul Kidby in the Discworld's Assassins' Guild Yearbook and Diary 2000, shows a youngish woman, athletic in build, who appears indeed to wear two swords: one conventionally scabbarded at the waist, and the other in a scabbard at her back, on the left shoulder, no doubt for a quick over-the-shoulder draw.
Observation
The Médaillon Des Deux Épées (Medal of the Two Swords in French) was a French military award created in 1771 and last awarded in 1795. Perhaps suggesting Madame has a family history of violent employment
Her name translates into English as "Madame Two-Swords", which aurally is not a million miles away from "Madame Tussauds", proprietor of a famous waxworks museum. Is this a built-in coincidence, which may be used to set up a joke in a forthcoming book? This could be a Quirmish nickname in the same style of Python's Arthur "Two Sheds" Jackson and John "Two Jags" Prescott. (The derivation from Tussauds {apostrophe officially renounced, another story} is more easily understood by those familiar with "fraffly-fraffly" or Rustian accents.)
Interesting point! In my fanfic, she is the daughter of a master swordmith... maybe in Dibbler style an ancestor, faced with slow trade, offered two swords for the price of one, et celui me tranche la gorge, chevalier.... and the name stuck. I can see the family forge, at the Sign of the Two Swords...
It also occurs to me that in writing this for the Assassins' Yearbook 2000 (pub. Dec 1999 for 2000), several years before Monstrous Regiment(2003) saw the light of day, Terry was perhaps playing with the central idea - of women in an unfair world pretending to be men so as to make a point or get a square deal - and he was experimenting with setting it in a different context. In the original draft, was Polly Perks intended to enroll in the Assassins' School by stealth, so as to make a point? The detail about socks is a giveaway... the text does say that any girl who got the full distance undetected and graduated as an Assassin was discreetly honoured with full Guild membership, rather than risk embarrassing publicity. Presumably those who were found out were expelled or otherwise Failed. Hmmm.... fanfic beckons...