Ask questions or just talk about different languages. Since BrainKing is an international game site supporting many languages, this board can be kind of useful.
Heard that in a quiz once. The answer they gave was that originally pants referred to fabric wrapped separately on each leg then wrapped or tied at the waist. Saying that trousers were from a Welsh word meaning tight shorts of some kind lol
Then you could mention tweezers, scissors or pliers. Let's face it English isn't the most straightforward of languages!