Sort-of memes that are cracking you up at the moment

not sure which trousers routinely came in two parts other than assless chaps

One thing I do know is that there were periods where armoured soldiers/knights would hang their trousers directly from their upper armour rather than tie them around their waists, and depending on the armour it wasn't always smart for the trousers to be a single item, in a "Oops, I just stood up out of my saddle to race a cheeky fella on a Brompton, only to find that the velcro in my bib shorts has attached to the wrong thing" fashion, one that didn't happen if they weren't joined at the crotch. Not going to google it, but pantaloons probably had a similar history at some point, which explains both pants and Americans. Aside from which, trousers, trews/pants/pantaloons could probably be classed as different names that people in different places or times gave to essentially the same thing, which could mean that even if a new name was given to what - at that point and forever after - was a single piece of clothing, the habit of referring to such things in the plural just carried on.