This link on the left gave me the old internet birdie, the 404. Which reminded me that my group, white guys, both outnumbers blacks and may even have more words of discrimination hurled our way. One thing I've noticed in travel has stumped all the learned guys I've badgered (pardon if my spelling is a little off)--

In Mexico, they call me a "gringo".
In Romania, they call me a "gadjo".
In Japan, they call me a "gaijin".

I know these guys aren't in cahoots (oops, another "hoot" word, maybe), so why do their terms of derision seem so similar?

so why do their terms of derision seem so similar?

It's a coincidence. Mexican Spanish gringo is usually thought to be from griego 'Greek'; Japanese 外人 (がいじん, gaijin), literally 'foreign person'. Gadjo is a Romani word, but I am not aware of an etymology.