I recently discovered that in North America generally “underwear” now is reduced to only mean underpants/ undershorts / knickers / briefs and not the whole range of lingerie or other garments you might put on before you donned jeans or skirt and shirt or sweater.
It some N Americans use “knicker” to mean knickerbockers (breeches cuffed below the knee), it amused me when they were briefly fashionable in the 80s
Marks and Spencer underwear department must confuse a few transatlantic travellers, especially at this time of year when the display seems to consist mainly of bright red lacy bras and camis (teddies).
And while we are in the underpinnings section, the US use of “vest” to mean a buttoned waistcoat rather than the kind of undergarment favoured by Marlon Brando in a Streetcar named Desire has always confused me. My father called his a singlet but it was usually a string vest
Going back to food, the different US grades of cream (heavy, light, half and half) always confuse being different from ours (double, whipping, single) and I’ve given up trying to understand French cream!