You're right winner. The proper term for them is: Espaldas mojadas.
In my day I've crossed a few international borders.Many,many borders in fact.I have never,*ever* violated any country's immigration laws,not even Australia's,a nation that denied my application for a "green card".And,in return,I don't expect *any* foreigner to violate the immigration laws of *my* country.Not one! I will not tolerate it,I will not look the other way!
I'm afraid I have to tell you that I'll continue to use that word so that I might avoid using the words I *truly* want to use...words that would certainly get me banned from FR for life.
Sorry if you're offended.