[nottorp]

> if you're collecting zip codes you are already assuming United States

From outside the US: I always thought "zip code" is just what you USers call a postal code. I only found out it's a trademark today, from this HN discussion.

So most people outside the US will see "zip code" and think "oh, they mean postal code but they have this weird term for it".

[quesera]

It's "ZIP Code™", trademarked by the US Postal Service (this is mostly to prevent others from misusing the name). It is exactly equivalent to a postal code, and most US residents will know both terms, although they will always say "ZIP".

ZIP is an acronym for "Zone Improvement Plan", but no one knows that and it's not meaningful if you do!