A friend consulted for an English firm on a Johannesburg project for a while and became used to hearing and using South African English slang for a number of things. This was back in the Dark Ages when floppy disks were the standard for storing electronic information.
Once he was back in London briefing the consulting firm, he realized he was out of floppy disks and went to the London office manager to request some. He thought it would be acceptable (as well as secretly cool) by using the South African slang term for what he needed: a stiffy.
My father worked in a fairly formal office setting in Munich when I was a kid. His German accent wasn't the greatest, but his vocabulary and grammar were excellent.
His German improved enough during that year that he was able to make jokes and be understood - and actually get laughs....but sometimes the best of intentions can backfire on a person who isn't familiar with euphemisms in another language.
Someone in the office paid him a compliment about being a nice person, and his response was to say that he was "a warm fellow". Conversation came to a screeching halt.
Another co-worker overheard the exchange and discretely asked him if he meant to disclose that he was a homosexual. (This was 1973 - not exactly a progressive year for gay tolerance anywhere.)
Another friend, also working in London, needed to get to another location of his firm's office. He didn't have a car, but he knew there was a good chance someone else would be driving there.
So in an effort to keep things green by carpooling, he emailed about 30 people to let them know he needed to get to Wembley...and that he needed a ride.
Every last person emailed immediately back with various responses:
"Um, would oblige but am not gay."
"Well, don't we ALL."
"You did *not* just circulate that email to everyone, did you??"
"Oh, Mike.....you stupid Yank."
"Let me first ask my husband's permission."
"We don't condone sexual harassment of any nature in this office."
A German friend of mine came to visit when I lived in D.C. I knew he enjoyed flying and held a pilot's license, so I enthused about taking him to the Air & Space Museum. To my surprise, his interest in going was lukewarm at best. After my third suggestion of seeing it, he asked me "what exactly is there to see at this museum?"
I listed everything that I could remember about space flight and the history of flying and Amelia Earhart and the moon rocks and Charles Lindbergh and the Apollo rocket replicas, etc., and this joyous look of comprehension came over his face. He thought I'd been saying "the Aaron Space Museum" and hadn't a clue what it was all about.
To this day he still tells me to give his best regards to Aaron Space.