1. Use the cheat CreateItem("killsw01"); this will spawn a Long Sword +2.
2. Equip your main character with that Long Sword +2. (Don't worry if your main character can't equip Long Swords; they will be able to equip this one anyway.)
3. While the sword is equipped, get a game over. (Note that the sword has to be active for this to work; if the weapon is swapped for another, or if a magically created weapon (including those created by polymorph effects) is active at the time of the game over, it won't count.
If you can do this, you will then unlock the ability to equip pants.
(On a more serious note, if you actually try this, you will find step 3 to be harder than you might expect (assuming you aren't familiar with the mentioned cheat).)
Edit: Added missing parenthesis.
Edit 2: Why was this post "low rated"?