Underwear is symptomatic of a big problem in society these days - it has hundreds of names that can be used to colloquially refer to them. While some people may use this to their advantage, others (us included) often get lost in a conversation and then have to bow out quietly.
Here is a list of 25 names that are commonly used to refer to undies.
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No one in their right mind would blame you if you didn't understand someone was referring to your underwear if they mentioned your 'Johnson Holders' or 'Pudding Hammock.' However, it is the 21st Century, so you have to be prepared for this. Junkmail's recommendation:
Have 3 words prepared that could be used to refer to anything and everything (for example: deck chairs), and refer to the item you are unsure about with them. There is every chance that the person who first used the weird colloquial term will want to look cool, and giggle along politely, while feeling insecure about what they were actually laughing at. 1 point to you.