What do Americans call nappies

early 14c., from O.Fr. diapre "ornamental cloth," from M.L. diasprum, from Medieval Gk. diaspros, from dia- "entirely, very" + aspros "white." Aspros originally meant "rough," and was applied to the raised parts of coins (among other things), and thus was used in Byzantine Gk. to mean "silver coin," from which the bright, shiny qualities made it an adj. for "whiteness." Modern sense of "underpants for babies" is continuous since 1837, but such usage has been traced back to 1590s.

nappy1

n pl -pies

Brit a piece of soft material, esp towelling or a disposable material, wrapped around a baby in order to absorb its excrement Also called napkin US and Canadian name diaper

[changed from napkin]

Apparently we used to call them napkins, which is where "nappy" came from, before about 1837. The US and Canada changed to "diaper" at some point. It was probably another case of creating an euphemism for something unpleasant. There are many different euphemisms between different places for unpleasant or embarrassing things; how many different words can there be for toilet and bathroom, for instance? There's a different word for it depending on what English speaking country you are in, what region you are in, etc. If you are aboard a ship it is the "head." Diapers are closely related to bathrooms, in a way, so it's not surprising that there would be different words for them.

It might also come from a marketing idea, if a company thought that selling "napkins" would be somewhat ambiguous. Or it could be that people didn't want to call the thing they wipe their faces with by the same name that they called the thing they wipe a babies rear end with.

Source(s): http://www.etymonline.com/index.php?term=diaperhttp://www.thefreedictionary.com/nappy