Although I do my best to be a gentleman, there are times when I've inadvertantly been less than chivalrous to the opposite sex during my years in Japan. I learned early on that reading manga was a good way to help my Japanese improve since it offers "living" examples of spoken language you won't find in a textbook...though the series I chose was the post-apocalyptic Fist of the North Star, which lead to some embarrassment when talking with Japanese females while I un-learned all the hilariously manly-sounding words. Gaijin-in-Japan Rule #26 states that the likelihood of mis-pronouncing the word "mango" goes up the prettier your waitress is, and most foreigners in Japan have made this particular faux pas. For women the line between oneesan (meaning older sister, or a young woman aged 18-25 or so) and obasan ("aunt," or any older woman above the age of 35) can be a fine one, and I've accidentally caused offense by choosing the wrong word for a person I was addressing. Then a couple of months ago I was walking in Akihabara and happened by a shop where two female employees were showing off Apple's iPhone 4S. I'd been meaning to try the just-released Japanese version of the Siri "voice assistant," so I asked the girls to show me Siri...which lead to a gasp of shock, since Siri (pronounced shiri) means "butt" in Japanese, and the shop employees apparently had not known about this feature of the iPhone.
Siri (shiri) means "butt" in Japanese.