An immigrant invited his entire church to have dinner at his home so they could "all be in a family way together," not realizing this is a euphemism for pregnancy.
In both German and French, douche means shower. In English, it is a word used for cleaning female genitals, often with some medicinal purpose. I have known a German woman who couldn't understand how a vinegar and water douche was supposed to help with her vaginal yeast infection. She also wanted the doctor to explain how you get your shower to put out a mix of vinegar and water.
A tiny little French teacher of mine did a year of study in Paris. At some big dinner as everyone passed around one course after another, she reached a point where she was too full to eat another bite. She translated "I'm full" into French (Je sui pleine) and all conversation at the table came to a dead halt as this is a very vulgar expression for pregnancy along the lines of "I'm knocked up." Then they realized it was a weird Americanism and moved on.